ACE / ULEIS Summary Bibliography

 

1) Refereed publications

 

1.         Mason, G. M., R. E. Gold, S. M. Krimigis, J. E. Mazur, G. B. Andrews, K. A. Daley, J. R. Dwyer, K. F. Heuerman, T. L. James, M. J. Kennedy, T. LeFevere, H. Malcolm, B. Tossman, and P. H. Walpole, “The Ultra-Low Energy Isotope Spectrometer (ULEIS) for the ACE spacecraft”, Space Sci. Rev., 86, 409-448, 1998.

 

2.         Mason, G. M., C. M. S. Cohen, A. C. Cummings, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, J. E. Mazur, R. A. Mewaldt, E. Möbius, M. Popecki, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Particle acceleration and sources in the November 1997 solar energetic particle events”, Geophys. Res. Letters, 26, 141-144, 1999.

 

3.         Mason, G. M., J. E. Mazur, and J. R. Dwyer, “³He enhancements in large solar energetic particle events”, Astrophys. J. (Letters), 525, L133-L136, 1999.

 

4.         Dwyer, J. R., G. M. Mason, M. I. Desai, J. E. Mazur, and T. T. von Rosenvinge, “The spatial structure of ion events measured upstream of the Earth’s bow shock by ACE/ULEIS and WIND/STEP”, Geophys. Res. Letters, 27, 65-68, 2000.

 

5.         Mazur, J. E., G. M. Mason, J. R. Dwyer, J. Giacalone, J. R. Jokipii, and E. C. Stone, “Interplanetary magnetic field line mixing deduced from impulsive solar-flare particles”, Astrophys. J. (Letters), 532, L79-L82, 2000.

 

6.         Giacalone, J., J. R. Jokipii, and J. E. Mazur, “Small-scale gradients and large-scale diffusion of charged particles in the heliospheric magnetic field”, Astrophys. J. (Letters), 532, L75-L78, 2000.

 

7.         Mazur, J. E., G. M. Mason, J. R. Dwyer, J. Giacalone, J. R. Jokipii, and E. C. Stone, “The mixing of interplanetary magnetic field lines: a significant transport effect in studies of the energy spectra of impulsive flares”, in The acceleration and transport of energetic particles observed in the heliosphere: ACE 2000 Symposium, R. A. Mewaldt, E. Möbius and T. H. Zurbuchen, Editors, 2000, CP528, AIP Press: New York. pp. 47-54. (invited review)

 

8.         Ho, G. C., E. C. Roelof, G. M. Mason, R. E. Gold, S. M. Krimigis, and J. R. Dwyer, “Heavy ions in ³He enhanced solar energetic particle events”, in The acceleration and transport of energetic particles observed in the heliosphere: ACE 2000 Symposium, R. A. Mewaldt, E. Möbius and T. H. Zurbuchen, Editors, 2000, CP528, AIP Press: New York. pp. 99-102.

 

9.         Möbius, E., B. Klecker, M. A. Popecki, D. Morris, G. M. Mason, E. C. Stone, A. Bogdanov, J. R. Dwyer, A. B. Galvin, H. Heirtzler, D. Hovestadt, L. M. Kistler, and C. Siren, “Survey of ionic charge states of solar energetic particle events during the first year of ACE”, in The acceleration and transport of energetic particles observed in the heliosphere: ACE 2000 Symposium, R. A. Mewaldt, E. Möbius and T. H. Zurbuchen, Editors, 2000, CP528, AIP Press: New York. pp. 131-134.

 

10.     Giacalone, J., J. R. Jokipii, and J. E. Mazur, “Solar energetic particles vs. global cosmic-ray diffusion”, in The acceleration and transport of energetic particles observed in the heliosphere: ACE 2000 Symposium, R. A. Mewaldt, E. Möbius and T. H. Zurbuchen, Editors, 2000, CP528, AIP Press: New York. pp. 157-160.

 

11.     Mason, G. M., “Composition and energy spectra of ions accelerated in corotating interaction regions”, in The acceleration and transport of energetic particles observed in the heliosphere: ACE 2000 Symposium, R. A. Mewaldt, E. Möbius and T. H. Zurbuchen, Editors, 2000, CP528, AIP Press: New York. pp. 234-241. (invited review)

 

12.     Mason, G. M., J. R. Dwyer, and J. E. Mazur, “New properties of ³He-rich flares deduced from low energy particle spectra”, Astrophys. J. (Letters), 545, L157-L160, 2000.

 

13.     Ho, G. C., E. C. Roelof, S. E. Hawkins, III, R. E. Gold, G. M. Mason, J. R. Dwyer, and J. E. Mazur, “Energetic electrons in ³He-enhanced solar energetic particle events”, Astrophys. J., 552, 863-870, 2001.

 

14.     Desai, M. I., G. M. Mason, J. R. Dwyer, J. E. Mazur, C. W. Smith, and R. M. Skoug, “Acceleration of ³He nuclei at interplanetary shocks”, Astrophys. J. (Letters), 553, L89-L92, 2001.

 

15.     Mason, G. M., “Heliospheric lessons for galactic cosmic ray acceleration”, Space Sci. Rev., 99, 119-133, 2001. (Invited review)

 

16.     Smith, C. W., N. G. Ness, L. F. Burlaga, R. M. Skoug, D. J. McComas, T. H. Zurbuchen, G. Gloeckler, D. K. Haggerty, R. E. Gold, M. I. Desai, G. M. Mason, J. E. Mazur, J. R. Dwyer, M. A. Popecki, E. Möbius, C. M. S. Cohen, and R. A. Leske, “ACE observations of the Bastille Day 2000 Interplanetary Disturbances”, Solar Phys., 204, 229-254, 2001.

 

17.     Mewaldt, R. A., G. M. Mason, G. Gloeckler, E. R. Christian, C. M. S. Cohen, A. C. Cummings, A. J. Davis, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, J. E. Mazur, E. C. Stone, T. T. von Rosenvinge, M. E. Wiedenbeck, and T. H. Zurbuchen, “Long-term fluences of energetic particles in the heliosphere”, in “Solar and Galactic Composition -- a joint SOHO/ACE workshop”, R. F. Wimmer- Schweingruber, Editor, 2001, CP598, AIP Press: New York. p 165-170.

 

18.     Mewaldt, R. A., R. C. Ogliore, G. Gloeckler, and G. M. Mason, “A new look at Neon-C and SEP Neon”, in “Solar and Galactic Composition -- a joint SOHO/ACE workshop”, R. F. Wimmer-Schweingruber, Editor, 2001, CP598, AIP Press: New York. p 393-398.

 

19.     Dwyer, J. R., G. M. Mason, J. E. Mazur, R. E. Gold, S. M. Krimigis, E. Möbius, and M. Popecki, “Isotopic Composition of Solar Energetic Particle Events Measured by Advanced Composition Explorer/ULEIS”, Astrophys. J., 563, 403-409, 2001.

 

20.     Mason, G. M., J. E. Mazur, and J. R. Dwyer, “A new heavy ion abundance enrichment pattern in ³He-rich solar particle events”, Astrophys. J. (Letters), 565, L51-L54, 2002.

 

21.     Mason, G. M., M. E. Wiedenbeck, J. A. Miller, J. E. Mazur, E. R. Christian, C. M. S. Cohen, A. C. Cummings, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, R. A. Mewaldt, P. L. Slocum, E. C. Stone, and T. T. von Rosenvinge, “Spectral properties of He and heavy ions in ³He-rich solar flares”, Astrophys. J., 574, 1039-1058, 2002.

 

22.     Tylka, A. J., P. R. Boberg, C. M. S. Cohen, W. F. Dietrich, C. G. Maclennan, G. M. Mason, C. K. Ng, and D. V. Reames, “Flare- and Shock-Accelerated Energetic Particles in the Solar Events of 2001 April 14 and 15”, Astrophys. J.(Letters), 581, L119-L123, 2002.

 

23.     Desai, M. I., G. M. Mason, J. R. Dwyer, J. E. Mazur, R. E. Gold, S. M. Krimigis, C. W. Smith, and R. M. Skoug, “Evidence for a suprathermal seed population of heavy ions accelerated by interplanetary shocks near 1 AU”, Astrophys. J., 588, 1149-1162, 2003.

 

24.     Ho, G. C., G. M. Mason, E. C. Roelof, R. E. Gold, and J. E. Mazur, “Peak proton intensities and composition variations of heavy ions during large solar energetic particle events: ULEIS observations”, Adv. Space. Res., 32, 561-566, 2003.

 

25.     Slocum, P. L., E. C. Stone, R. A. Leske, E. R. Christian, C. M. S. Cohen, A. C. Cummings, M. I. Desai, J. R. Dwyer, G. M. Mason, J. E. Mazur, R. A. Mewaldt, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Elemental fractionation in small solar energetic particle events”, Astrophys. J., 594, 592-604, 2003.

 

26.     Ho, G., C., E. C. Roelof, G. M. Mason, D. Lario, R. E. Gold, J. R. Dwyer, and J. E. Mazur, “Composition Variations in Large Solar Energetic Particle Events”, Solar Wind 10, ed. M. Velli, R. Bruno, and F. Malara, CP679, 624-627, 2003.

 

27.     Ho, G. C., E. C. Roelof, G. M. Mason, D. Lario, and J. E. Mazur, “Onset study of impulsive solar energetic particle events”, Adv. Space. Res., 32, 2679-2684, 2003.

 

28.     Mason, G. M., J. E. Mazur, J. R. Dwyer, J. R. Jokipii, R. E. Gold, and S. M. Krimigis, “Abundances of heavy and ultra-heavy ions in ³He-rich solar flares”, Astrophys. J., 606, 555-564, 2004.

 

29.     Desai, M. I., G. M. Mason, M. E. Wiedenbeck, C. M. S. Cohen, J. E. Mazur, J. R. Dwyer, R. E. Gold, S. M. Krimigis, Q. Hu, C. W. Smith, and R. M. Skoug, “Spectral properties of heavy ions accelerated by interplanetary shocks near 1 AU”, Astrophys. J., 611, 1156-1174, 2004.

 

30.     Liu, S., V. Petrosian, and G. M. Mason, “Stochastic acceleration of ³He and ⁴He by parallel propagating plasma waves”, Astrophys. J. (Letters), 613, L81-L84, 2004.

 

31.     Emslie, A. G., H. Kucharek, B. R. Dennis, N. Gopalswamy, G. D. Holman, G. H. Share, A. Vourlidas, T. G. Forbes, P. T. Gallagher, G. M. Mason, T. R. Metcalf, R. A. Mewaldt, R. J. Murphy, R. A. Schwartz, and T. H. Zurbuchen, “Energy partition in two solar flare/CME events”, J. Geophys. Res., 109, A10104, doi:10.1029/2004JA010571, 2004.

 

32.     Ho, G. C., E. C. Roelof, and G. M. Mason, “Upper limit on ³He fluence in solar energetic particle events”, Astrophys. J. (Letters), 621, L141-L144, 2005.

 

33.     Li, G., G. P. Zank, M. I. Desai, G. M. Mason, and W. K. M. Rice, “Particle acceleration and transport at CME-driven shocks: a case study”, in “Particle Acceleration in Astrophysical Plasmas: Geospace and Beyond”, (D. L. Gallagher, J. L. Horwitz, J. D. Perez, R. D. Preece, and J. J. Quenby, editors), Geophysical Monograph 156, (AGU: Washington), pp 51-58, 2005.

 

34.     Cohen, C. M. S., R. A. Mewaldt, R. A. Leske, A. C. Cummings, E. C. Stone, G. M. Mason, M. I Desai, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Heavy ion abundances and spectra from the large SEP events of October-November 2003”, J. Geophys. Res., 110, doi:10.1029/2005JA011004, 2005.

 

35.     Mewaldt, R. A., and G. M. Mason, “Cosmic Rays in the Galaxy and the Heliosphere”, in “The Solar System and Beyond -- Ten Years of ISSI”, (J. Geiss, and Bengt Hultqvist, editors), European Space Agency Publication Division, SR-003 (ISBN: 1608-280X) , pp. 69-81, 2005.

 

36.     Qin, G., M. Zhang, J. R. Dwyer, H. K. Rassoul, and G. M. Mason, “The model dependence of solar energetic particle mean free paths under weak scattering”, Astrophys. J. (Letters), 627, 562-566, 2005.

 

37.     Mewaldt, R. A., C. M. S. Cohen, A. W. Labrador, R. A. Leske, G. M. Mason, M. I. Desai, M. D. Looper, J. E. Mazur, R. S. Selesnick, and D. K. Haggerty, “Proton, helium, and electron spectra during the large solar particle events of October, November 2003”, J. Geophys. Res., 110, doi:10.1029/2005JA011038, 2005.

 

38.     Channok, M., D. Ruffolo, M. I. Desai, and G. M. Mason, “Finite-time shock acceleration of energetic storm particles”, Astrophys. J. (Letters), 633, L53-L56, 2005.

 

39.     Mason, G. M., M. I. Desai, J. E. Mazur, and J. R. Dwyer, “Energetic particles accelerated by shocks in the heliosphere:  what is the source material?”, in “Physics of Collisionless shocks”, G. Li, G. P. Zank, and C. T. Russell, Editors, 2005, CP781, AIP Press:  New York, 219-226, 2005. (see also invited talk #49).

 

40.     Mewaldt, R. A., C. M. S. Cohen, G. M. Mason, A. W. Labrador, M. L. Looper, D. E. Haggerty, C. G. Maclennan, A. C. Cummings, M. I. Desai, R. A. Leske, G. Li, J. E. Mazur, E. C. Stone, and M. E. Wiedenbeck, “Solar Energetic Particle Spectral Breaks”, in “Physics of Collisionless shocks”, G. Li, G. P. Zank, and C. T. Russell, Editors, 2005, CP781, AIP Press:  New York, p 227-232, 2005. (see also invited talk #50).

 

41.     Liu, S., V. Petrosian, and G. M. Mason, “Stochastic acceleration of ³He and ⁴He by parallel propagating plasma waves:  general results”, Astrophys. J., 636, 462-474, Jan. 2006.

 

42.     Wang, Y.-M., M. Pick, and G. M. Mason, “Coronal holes, jets, and the origin of ³He-rich particle events”, Astrophys. J., 639, 495-509, March 2006.

 

43.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “Solar cycle variations of suprathermal heavy ion population near 1 AU”, Astrophys. J. (Letters), 645, L81-L84, July 2006a.

 

44.     Dröge, W., J. J. Kartavykh, B. Klecker, and G. M. Mason, “Acceleration and transport modeling of solar energetic particle charge states for the event of 1998 September 9”, Astrophys. J., 645, 1516-1524, July 2006.

 

45.     Mason, G. M., M. I. Desai, C. M. S. Cohen. R. A. Mewaldt, E. C. Stone, and J. R. Dwyer, “The role of interplanetary scattering in western hemisphere large solar energetic particle events”, Astrophys. J. (Letters), 647, L65-L68, Aug. 2006.

 

46.     Pick, M., G. M. Mason, Y. -M. Wang, C. Tan, and L. Wang, “Solar source regions for ³He-rich solar energetic particle events identified using imaging radio, optical, and energetic particle observations”, Astrophys. J., 648, 1247-1255, Sept. 2006.

 

47.     Desai, M. I., G. M. Mason, R. E. Gold, S. M. Krimigis, C. M. S. Cohen, R. A. Mewaldt, J. E. Mazur, and J. R. Dwyer, “Heavy ion elemental abundances in large solar energetic particle events and their implication for the seed population”, Astrophys. J., 649, 470-489, Sept. 2006.

 

48.     Mewaldt, R. A., C. M. S. Cohen, and G. M. Mason, “The source material for large solar energetic particle events”, in Solar eruptions and energetic particles, (N. Gopalswamy, R. A. Mewaldt, and J. Torsti, eds.), American Geophysical Union Monograph Series, Vol. 165, ISBN 0-87590-430-0, pp. 115-126, Oct. 2006.

 

49.     Mazur, J. E., J. B. Blake, P. L. Slocum, M. K. Hudson, and G. M. Mason, “The creation of new ion radiation belts associated with solar energetic particle events and interplanetary shocks”, in Solar eruptions and energetic particles, (N. Gopalswamy, R. A. Mewaldt, and J. Torsti, eds.), American Geophysical Union Monograph Series, Vol. 165, ISBN 0-87590-430-0, pp. 345-352, Oct. 2006.

 

50.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “The seed population for energetic particles accelerated by CME-driven shocks”, Space. Sci. Rev., 124, 261-275, June 2006.  (Space Sciences Series of ISSI, Vol. 22).

 

51.     Cohen, C. M. S., R. A. Mewaldt, R. A. Leske, A. C. Cummings, E. C. Stone, M. E. Wiedenbeck, T. T. von Rosenvinge, and G. M. Mason, “Solar elemental composition based on studies of Solar Energetic Particles”, Space Sci. Rev., 130, 183-194, DOI 10.1007/s11214-007-9218-y, Sept. 2007.

 

52.     Mewaldt, R. A., C. M. S. Cohen, A. C. Cummings, G. M. Mason, M. I. Desai, R. A. Leske, J. Raines, E. C. Stone, M. E. Wiedenbeck, T. T. von Rosenvinge, and T. H. Zurbuchen, “On the differences in composition between Solar Energetic Particles and the Solar Wind”, Space Sci. Rev., 130, 207-219, DOI 10.1007/s11214-007-9187-1, Sept. 2007.

 

53.     Mason, G. M., “³He-rich Solar Energetic Particle Events”, Space Sci. Rev., 130, 231-242, DOI 10.1007/s11214-007-9156-8, Sept. 2007.

 

54.     Desai, M. I., G. M. Mason, R. E. Gold, S. M. Krimigis, C. M. S. Cohen, R. A. Mewaldt, J. E. Mazur, and J. R. Dwyer, “Evidence for a two-stage acceleration process in Large Solar Energetic Particle Events,” Space Sci. Rev., 130, 243-253, DOI 10.1007/s11214-007-9219-x, Sept. 2007.

 

55.     Kartavykh, Y. Y., W. Dröge, B. Klecker, G. M. Mason, E. Möbius, M. Popecki, and S. Krucker, “Evidence for a two-temperature source region in the ³He-rich solar energetic particle event of 2000 May 1st”, Astrophysical J., 671, 947-954, August 2007.

 

56.     DiFabio, R., E. Möbius, M. Popecki, G. M. Mason, B. Klecker, and H. Kucharek, “Energy dependent charge states and their connection with ion abundances in impulsive solar energetic particle events”, Astrophys. J., submitted, May 2006.

 

57.     Kocharov, L., J. Laivola, G. M. Mason, L. Didkovsky, and D. J. Judge, “Extended 3He-rich periods of solar energetic particles in structured solar wind”, Astrophys. J., accepted, Nov. 2007.

 

58.     Allegrini, F., M. I. Desai, G. M. Mason, H. Kucharek, and E. Möbius, “Evidence for mass-per-charge dependent acceleration of a multiple-component seed population by CME-driven interplanetary shocks near 1 AU”, Astrophys. J., submitted, Oct. 25, 2007.

 

59.     Desai, M. I., G. M. Mason, R. Müller-Mellin, A. Korth, U. Mall, J. R. Dwyer, and T. T. von Rosenvinge, “The spatial distribution of upstream ion events from the Earth’s bow shock measured by ACE, Wind, and STEREO”, J. Geophys. Res., submitted, Oct, 24, 2007.

 

60.     Mason, G. M., R. A. Leske, M. I. Desai, C. M. S. Cohen, J. R. Dwyer, J. E. Mazur, R. A. Mewaldt, R. E. Gold, and S. M. Krimigis, “Abundances and energy spectra of corotating interaction region heavy ions observed during solar cycle 23”,  Astrophys. J., accepted, January 17,  2008.

 

61.     127.  Nitta, N., G. M. Mason, M. E. Wiedenbeck, C. M. S. Cohen, S. Krucker, I. Hannah, M. Shimojo, and K. Shibata, “Coronal Jet Observed by Hinode as the Source of a ³He-rich Solar Energetic Particle Event”, Astrophys. J., accepted, January 22, 2008.

 

 

 

 

2)  Conference proceedings

 

1.         Powell, F. R., R. A. M. Keski-Kuha, M. V. Zombeck, R. E. Goddard, G. Chartas, L. K. Townsley, E. Möbius, J. M. Davis, and G. M. Mason, “Metalized polyimide filters for X-ray astronomy and other applications”, invited review paper, Proc. SPIE (The International Society for Optical Engineering) annual meeting, July-1 August 1997, San Diego, California, USA, 3113, 432-440, 1997.

 

2.         Mason, G. M., J. R. Dwyer, J. E. Mazur, R. E. Gold, and S. M. Krimigis, “Spectral forms in ³He-rich solar particle events”, Proc. 26^th Internat. Cosmic Ray Conf. (Salt Lake City, USA), 6, 103-106, 1999.

 

3.         Mason, G. M, C. M. S. Cohen, A. C. Cummings, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, J. E. Mazur, R. A. Mewaldt, E. Möbius, M. Popecki, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Particle acceleration and sources in the November 1997 solar energetic particle events”, Proc. 26^th Internat. Cosmic Ray Conf. (Salt Lake City, USA), 6, 115-118, 1999. (same as journal publication #2).

 

4.         Dwyer, J. R., G. M. Mason, J. E. Mazur, R. E. Gold, and S. M. Krimigis, “Isotopic composition of SEP Ne as measured by ACE/ULEIS”, Proc. 26^th Internat. Cosmic Ray Conf. (Salt Lake City, USA), 6, 147-150, 1999.

 

5.         Christian, E. R., W. R. Binns, J. B. Blake, C. M. S. Cohen, A. C. Cummings, D. C. Hamilton, M. E. Hill, P. L. Link, E. Keppler, S. M. Krimigis, R. A. Leske, M. D. Looper, R. G. Marsden, G. M. Mason, J. E. Mazur, R. A. Mewaldt, T. R. Sanderson, E. C. Stone, T. T. von Rosenvinge, M. E. Wiedenbeck, and N Yanasak, “Observations of the Solar Modulation of Galactic and Anomalous Cosmic Rays During Solar Minimum”, Proc. 26^th Internat. Cosmic Ray Conf. (Salt Lake City, USA), 7, 519-522, 1999.

 

6.         Desai, M. I., G. M. Mason, J. R. Dwyer, J. E. Mazur, C. W. Smith, and R. M. Skoug, “Acceleration of ³He nuclei at interplanetary shocks”, Proc. 27^th Internat. Cosmic Ray Conf. (Hamburg, Germany), 9, 3612-3615, 2001.

 

7.         Mewaldt, R. A., C. M. S. Cohen, G. M. Mason, M. I. Desai, R. A. Leske, J. E. Mazur, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Impulsive flare material: a seed for large solar particle events?”, Proc. 28^th Internat. Cosmic Ray Conf, (Tsukuba, Japan), 6, 3229-3232, 2003.

 

8.         Klecker, B., M. A. Popecki, E. Möbius, M. I. Desai, G. M. Mason, and R. F. Wimmer-Schweingruber, “On the energy dependence of ionic charge states”, Proc. 28^th Internat. Cosmic Ray Conf, (Tsukuba, Japan), 6, 3277-3280, 2003.

 

9.         Popecki, M. A., J. E. Mazur, E. Möbius, B. Klecker, A. Bogdanov, G. M. Mason, and L. M. Kistler, “Observations of Energy-Dependent Charge States in Solar Energetic Particle Events”, Proc. 28^th Internat. Cosmic Ray Conf, (Tsukuba, Japan), 6, 3283-3286, 2003.

 

10.     Ho, G. C., E. C. Roelof, G. M. Mason, D. Lario, R. E. Gold, J. R. Dwyer, and J. E. Mazur, “Composition Variations in Large Solar Energetic Particle Events”, Proc. Tenth Solar Wind Conf., Pisa, Italy, June 17-21, 2002, M. Velli, R. Bruno, R. Malara, Eds., CP679, AIP Press: New York, pp. 624-627, 2003.

 

11.     Lario, D., G. C. Ho, R. B. Decker, E. C. Roelof, M. I. Desai, and C. W. Smith, “ACE observations of energetic particles associated with transient interplanetary shocks”, Proc. Tenth Solar Wind Conf., Pisa, Italy, June 17-21, 2002, M. Velli, R. Bruno, R. Malara, Eds., CP679, AIP Press: New York, pp. 640-643, 2003.

 

12.     Wiedenbeck, M. E., G. M. Mason, E. R. Christian, C. M. S. Cohen, A. C. Cummings, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, R. A. Mewaldt, J. E. Mazur, P. L. Slocum, E. C. Stone, and T. T. von Rosenvinge, “How Common is Energetic ³He in the Inner Heliosphere?”, Proc. Tenth Solar Wind Conf., Pisa, Italy, June 17-21, 2002, M. Velli, R. Bruno, R. Malara, Eds., CP679, AIP Press: New York, pp. 652-655, 2003.

 

13.     Mewaldt, R. A., C. M. S. Cohen, G. M. Mason, D. K. Haggerty, M. D. Looper, A. Vourlidas, M. I. Desai, J. Giacalone, A. W. Labrador, R. A. Leske, and J. E. Mazur, “How efficient are Coronal Mass Ejections at Accelerating Solar Energetic Particles?” Proceedings of the Solar Wind 11/SOHO 16 Conference, Connecting Sun and Heliosphere, 12-17 June 2005, Whistler, Canada, ESA SP-592, eds. T. H. Zurbuchen and B. Fleck, pp. 67-70, September 2005.

 

14.     Ho, G. C., D. Lario, R. B. Decker, M. I. Desai, Q. Hu, J. Kasper, and A.-F. Viñas, “Multi-spacecraft Observations of Interplanetary Shock Accelerated Particle Events,” Proceedings of the Solar Wind 11/SOHO 16 Conference ,Connecting Sun and Heliosphere, 12-17 June 2005, Whistler, Canada, ESA SP-592, eds. T. H. Zurbuchen and B. Fleck, pp. 421-424, September 2005.

 

15.     Wang, L., R. P. Lin, S. Krucker, and G. M. Mason, “A study of the solar injection for eleven impulsive electron/3He-rich SEP events”, Solar Wind 11/SOHO 16 conference, Connecting the Sun and Heliosphere Conference, 2005ESASP.592E..81W, Whistler, Canada, June 12-17, 2005.

 

16.     Király, P., G. M. Mason, R. A. Mewaldt, A. Posner, and J. Rodríguez-Pacheco, “Energy dependence of cumulative suprathermal and energetic particle fluence plots”, 29^th International Cosmic Ray Conference, Pune, India, session SH 1.2, Aug. 3-10, 2005.

 

17.     Király, P., W. I. Axford, E. I. Daibog, B. Heber, R. Kallenbach, K. Kecskeméty, G. M. Mason, Yu. I. Logachev, R. A. Mewaldt, A. Posner, J. Rodríguez-Pacheco, R. Treumann, and M. A. Zeldovich, “Solar and heliospheric sources of suprathermal and energetic particle populations”, 29^th International Cosmic Ray Conference, Pune, India, session SH 1.2, Aug. 3-10, 2005.

 

18.     Mewaldt, R. A., M. D. Looper, C. M. S. Cohen, G. M. Mason, D. K. Haggerty, M. I. Desai, A. W. Labrador, R. A. Leske, and J. E. Mazur, “Solar-Particle energy spectra during the large events of October-November 2003 and January 2005”, 29^th International Cosmic Ray Conference, Pune, India, session SH 1.2, Aug. 3-10, 2005

 

19.     Wiedenbeck, M. E., G. M. Mason, C. M. S. Cohen, A. C. Cummings, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. A. Leske, J. E. Mazur, R. A. Mewaldt, E. C. Stone, and T. T. von Rosenvinge, “The time variations of energetic 3He in interplanetary space from 1997 to 2005”, 29^th International Cosmic Ray Conference, Pune, India, session SH 1.2, Aug. 3-10, 2005.

 

20.     Mewaldt, R. A., C. M. S. Cohen, G. M. Mason, D. K. Haggerty, M. D. Looper, A. Vourlidas, M. I. Desai., J. Giacalone, A. W. Labrador, R. A. Leske, and J. E. Mazur, “What fraction of the kinetic energy of Coronal Mass Ejections goes into accelerating solar energetic particles?”, 29^th International Cosmic Ray Conference, Pune, India, session SH 1.3, Aug. 3-10, 2005

 

21.     Myasaka, H., E. C. Stone, R. A. Mewaldt, G. M. Mason, D. K. Haggerty, K. Nagata, J. Kikuchi, T. Doke, N. Hasebe, K. Maezawa, T. Takashima, A. Ihara, and A. Matsuoka, “ACE/NOZOMI Multispacecraft Observations of Solar Energetic Particles”, 29^th International Cosmic Ray Conference, Pune, India, session SH 2.1, Aug. 3-10, 2005.

 

22.     Channok, C., D. Ruffolo, M. I. Desai, and G. M. Mason, “Finite time shock acceleration and fits to ESP ion spectra”, 29^th International Cosmic Ray Conference, Pune, India, session SH 2.2, Aug. 3-10, 2005.

 

23.     Mewaldt, R. A., C. M. S. Cohen, D. K. Haggerty, G. M. Mason, M. L. Looper, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Radiation risks from large solar energetic particle events”, in “Turbulence and Nonlinear Processes in Astrophysical Plasmas”, G. Li, G. P. Zank, and C. T. Russell Editors, 2007, CP 932, AIP Press:  New York, pp. 277-282, 16-22 March 2007.

 

 

 

 

3)  Invited Papers

 

1.         Mason, G. M., A. C. Cummings, J. R. Dwyer, A. B. Galvin, R. E. Gold, D. Haggerty, E. Hawkins, D. Hovestadt, L. Kistler, B. Klecker, S. M. Krimigis, R. A. Leske, J. E. Mazur, R. A. Mewaldt, E. Möbius, M. Popecki, D. V. Reames, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Solar Energetic Particle Composition and Spectra During the November 1997 Solar Particle Events”, invited paper (20 min) presented at the Spring 1998 meeting of the American Geophysical Union, Trans. Am. Geophys. U., 79, S255, 1998.

 

2.         Mason, G. M., “New results from the ACE spacecraft on solar energetic particle acceleration and sources”, invited talk, 40 min., presented at the WE-Heraeus foundation seminar on Energetic Processes on the Sun and in the Heliosphere, Bad Honnef, Germany, October 18-21, 1998.

 

3.         Mason, G. M., “Particle acceleration and sources in the November 1997 solar energetic particle events”, invited talk, 20 min., presented at the Washington Area Astronomers 1998 Fall Meeting, Johns Hopkins University / Applied Physics Laboratory, Laurel, MD, Nov. 12, 1998.

 

4.         Mason, G. M., “Solar energetic particle events: solar maximum vs. solar minimum”, invited paper (20 min) presented at the Fall 1998 meeting of the American Geophysical Union, Trans. Am. Geophys. U., 79, F751, 1998.

 

5.         Mason, G. M., “The Sun and Heliosphere”, invited talk (30 min) presented at the American Astronautical Society 37^th Goddard Memorial Symposium, Greenbelt, MD, March 17-18, 1999.

 

6.         Dwyer, J. R., G. M. Mason, J. E. Mazur, R. E. Gold, and S. M. Krimigis, “Variability of Elemental and Isotopic Solar Energetic Particle Composition as Measured by ACE”, invited paper (20 min) presented at the Spring meeting of the American Geophysical Union, Boston, MA, May 1998, Trans. Am. Geophys. U., 80, S255, 1999.

 

7.         Mason, G. M., “Heliocentric lessons for Galactic Cosmic Ray Acceleration”, invited paper (45 min) presented at the International Space Science Institute (ISSI) workshop on The Astrophysics of Galactic Cosmic Rays, Bern, Switzerland, October 18-22, 1999

 

8.         Mazur, J. E., “Latest results from ACE on energetic particles from impulsive solar flares”, High Energy Solar Spectroscopic Imager (HESSI) Symposium, College Park, MD, October 18-22, 1999

 

9.         Mason, G. M., “Heliocentric energetic particles: source mixtures and other challenges of interpretation”, invited paper (20 min) presented at the 2^nd International Space Science Institute (ISSI) workshop on The Astrophysics of Galactic Cosmic Rays, Bern, Switzerland, May 15-19, 2000

 

10.     Mazur, J. E., “New insights into solar energetic particle composition”, invited paper (20 min) presented at the Fall 2000 Meeting of the American Geophysical Union, San Francisco, CA, Trans. Am. Geophys. U., 81, F953, 2000.

 

11.     Mason, G. M., “Solar energetic particle acceleration: new insights on impulsive and shock-related events”, invited paper (25 min) joint GEMSHINE 2001 Summer Workshop, Snowmass, Colorado, June 17-21, 2001.

 

12.     Mason, G. M., J. E. Mazur, and M. I. Desai, “Interplanetary recycling: the acceleration of suprathermals in CME-related solar particle events and interplanetary shocks”, invited paper (20 min) presented at the Fall 2001 meeting of the American Geophysical Union, San Francisco, CA, Trans. Am. Geophys. U., 82, F986, 2001.

 

13.     Mason, G. M., “Ions Accelerated in Corotating Interaction Regions: New Insights from Recent Measurements”, invited paper (25 min) presented at Workshop on Particle Transport and Acceleration in Cosmic Plasmas, IGPP, Univ. of California, Riverside, CA, Feb. 10-13, 2002.

 

14.     Mazur, J. E., G. M. Mason, J. R. Dwyer, J. Giacalone, J. R. Jokipii, and E. C. Stone, “Small-scale gradients and large-scale diffusion of solar flare particles in the inner heliosphere”, invited paper (25 min) presented at Workshop on Particle Transport and Acceleration in Cosmic Plasmas, IGPP, Univ. of California, Riverside, CA, Feb. 10-13, 2002.

 

15.     Mason, G. M., “3D Shock Propagation and Particle Acceleration: Insights from STEREO in-situ observations”, invited paper (20 min) presented at the First STEREO workshop: “The 3-d Sun and Inner Heliosphere: the STEREO View”, Ecole Polytechnique, Paris, France, March 18-20, 2002.

 

16.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “The Suprathermal Seed Population of Heavy Ions Accelerated at Interplanetary Shocks”, invited paper (25 min) presented at the Spring Meeting of the American Geophysical Union, Washington, DC, Trans. Am. Geophys. U., 83, paper SH42B-01, 2002.

 

17.     Slocum, P. L., E. R. Christian, C. M. S. Cohen, A. C. Cummings, R. A. Leske, J. E. Mazur, G. M. Mason, R. A. Mewaldt, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Energetic Particle Composition at 1 AU Between Large Gradual SEP Events”, invited paper (25 min) presented at the Spring Meeting of the American Geophysical Union, Washington, DC, Trans. Am. Geophys. U., 83, S266, Abstract SH42B-03, 2002.

 

18.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “The Suprathermal Seed Population for 0.05-10 MeV nucleon-1 Heavy Ions Accelerated at Interplanetary Shocks”, Invited paper (30 min), paper No. SIV-2, presented at SOLAR WIND 10, X Congresso Internazionale sul Vento Solare Palazzo dei Congressi, Università degli Studi, Pisa, Italy, June, 17-21 2002.

 

19.     Mazur, J. E., “The radiation environment inside and outside a spacecraft”, invited talk (75 min) presented at the IEEE Nuclear and Space Radiation Effects Conference (NSREC), Short Course Notebook, Phoenix, AZ, July 15-29, 2002 (68 pp).

 

20.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “Solar Cycle Dependence of the Suprathermal Seed Population of Heavy Ions Accelerated at Interplanetary Shocks”, Invited Paper (20 min.) presented at the SHINE Workshop, Banff, Canada, August 18-22, 2002.

 

21.     Mason, G. M., J. E. Mazur, M. I. Desai, and J. D. Dwyer, “Solar energetic particle acceleration: recent progress in shock-related and impulsive events”, Invited Paper (20 min) presented at the Huntsville 2002 Workshop on “Astrophysical Particle Acceleration in Geospace and Beyond”, October 6-10, 2002, Chattanooga, TN.

 

22.     Mazur, J. E., G. M. Mason, M. I. Desai, and J. D. Dwyer, “New Insights From Solar Energetic Particles at the Maximum of Cycle 23”, Invited Paper (20 min), Paper 02-A-01621, presented at the 34^th Scientific Assembly of the Committee on Space Research (COSPAR), Houston, TX, 10-19 October 2002.

 

23.     Mason, G. M., J. E. Mazur, M. I. Desai, and J. R. Dwyer, “Identifying the real seed population for shock accelerated energetic particles: recent observational progress”, Invited paper (20 min) presented at the Fall American Geophysical Union Meeting, San Francisco, Trans. Am. Geophys. U. (Fall Meet. Suppl.), 83, Abstract SH51B-10, 2002.

 

24.     Mason, G. M., “SEPs and shock particles: the May 12, 1997 MURI event”, Invited talk (10 min) presented at the MURI Workshop on the Coupling of SEP models to heliospheric models, University of Arizona, Tucson, AZ, March 17-18, 2003.

 

25.     Mason, G. M., M. I. Desai, J. E. Mazur, and J. R. Dwyer, “Evidence for a suprathermal seed population for solar energetic particles and the implications for modeling”, Invited paper (20 min) presented at the MURI Workshop on the Coupling of SEP models to heliospheric models, University of Arizona, Tucson, AZ, March 17-18, 2003.

 

26.     Desai, M. I., G. M. Mason, J. E. Mazur, J. R. Dwyer, R. E. Gold, S. M. Krimigis, C. W. Smith, and R. M. Skoug, “The suprathermal seed population of heavy ions accelerated by interplanetary shocks near 1 AU”, (30 minutes) Joint STEREO/PLASTIC/SOHO/CELIAS Workshop at Schwarszee, Switzerland, March 19, 2003.

 

27.     Desai, M. I., G. M. Mason, J. E. Mazur, J. R. Dwyer, R. E. Gold, S. M. Krimigis, R. M. Skoug, and C. W. Smith, “Elemental Abundances of Energetic Particles Inside Magnetic Clouds”, Invited Paper (20 min.) presented at the Solar, Heliospheric and Interplanetary Environment (SHINE) Workshop at Maui, Hawaii, July 6-11, 2003.

 

28.     Desai, M. I., G. M. Mason, J. E. Mazur, J. R. Dwyer, C. M. S. Cohen, E. C. Stone, R. A. Mewaldt, R. A. Leske, P. L. Slocum, E. R. Christian, T. T. von Rosenvinge, A. C. Cummings, M. E. Wiedenbeck, R. E. Gold, S. M. Krimigis, R. M. Skoug, and C. W. Smith, “Abundances and Energy Spectra of Heavy Ions Accelerated by Interplanetary Shocks Near 1 AU”, Invited Paper (20 min.) presented at the Solar, Heliospheric and Interplanetary Environment (SHINE) Workshop at Maui, Hawaii, July 6-11, 2003.

 

29.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “Contribution of flare particles to the suprathermal ion population through the solar cycle”, Invited Paper (20 min) presented at the ACE/RHESSI/WIND workshop, Taos, NM, Oct. 7-9, 2003.

 

30.     Mason, G. M., “Solar energetic particle acceleration and propagation: recent progress from ACE”, Invited Paper (20 min) presented at the ACE/RHESSI/WIND workshop, Taos, NM, Oct. 7-9, 2003

 

31.     Mewaldt, R. A., C. M. S. Cohen, M. I. Desai, R. E. Gold, S. M. Krimigis, A. W. Labrador, R. A. Leske, G. M. Mason, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “Solar Energetic Particle Observations during the Spectacular Solar Events of Late 2003”, Invited paper (20 min) presented at the Fall American Geophysical Union Meeting, San Francisco, Trans. Am. Geophys. U., 84, (Fall Meet. Suppl.), Abstract SM52G-03, 2003.

 

32.     Cohen, C. M. S., R. A. Mewaldt, G. M. Mason, M. I. Desai, A. C. Cummings, R. A. Leske, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “An Overview of SEPs During the October-November 2003 Storms”, Invited paper (20 min) presented at the Spring American Geophysical Union Meeting, Montreal, Trans. Am. Geophys. U., 85, Spring Meet. Suppl.), Abstract SH33A-01, 2004.

 

33.     Mason, G. M., J. E. Mazur, M. I. Desai, and J. R. Dwyer, “Solar energetic particles: recent observational progress for shock-related and impulsive events”, plenary talk (45 min.) presented at the NSF/SHINE 2004 meeting, Big Sky, Montana, June 28-July 2, 2004.

 

34.     Mason, G. M., J. E. Mazur, J. R. Dwyer, J. R. Jokipii, R. E. Gold, and S. M. Krimigis, “Abundances of heavy and ultra-heavy ions in ³He-rich solar flares”, invited talk (20 min.) presented at the NSF/SHINE 2004 meeting, Big Sky, Montana, June 28-July 2, 2004.

 

35.     Cohen, C. M. S., R. A. Mewaldt, G. M. Mason, M. I. Desai, A. C. Cummings, R. A. Leske, E. C. Stone, T. T. von Rosenvinge, and M. E. Wiedenbeck, “An overviewed of SEPs during the October-November 2003 Storms”, invited talk (20 min.) presented at the NSF/SHINE 2004 meeting, Big Sky, Montana, June 28-July 2, 2004.

 

36.     Desai, M. I., G. M. Mason, M. E. Wiedenbeck, C. M. S. Cohen, J. E. Mazur, J. R. Dwyer, R. E. Gold, S. M. Krimigis, Q. Hu, C. W. Smith, and R. M. Skoug, “Spectral Properties of Heavy Ions Accelerated by Interplanetary Shocks Near 1 AU”, invited talk (20 min.) presented at the NSF/SHINE 2004 meeting, Big Sky, Montana, June 28-July 2, 2004.

 

37.     Mason, G. M., M. I. Desai, J. E. Mazur, and J. R. Dwyer, “Recent Observational Progress in Identifying the Real Seed Population for Shock Accelerated Energetic Particles”, invited talk (20 min) presented at the 35^th COSPAR Scientific Assembly, Paris, France, 18-25 July 2004, Paper D1.3/E2.4-0031-04.

 

38.     Dwyer, J. R., G. M. Mason, M. I. Desai, and J. E. Mazur, “Observations of energetic particles associated with CIRs: using the composition and energy spectra to identify the source populations”, invited talk (20 min) presented at the 35^th COSPAR Scientific Assembly, Paris, France, 18-25 July 2004, Paper D1.3/E2.4-0014-04.

 

39.     Mazur, J. E., J. Blake, M. Looper, G. Mason, R. Mewaldt, and R. Leske, “The most intense SEP events of cycle 23: specifications and effects”, invited talk (20 min) presented at the 35^th COSPAR Scientific Assembly, Paris, France, 18-25 July 2004. Paper D2.5/E3.5-0043-04.

 

40.     Cohen, C. M. S., R. A. Mewaldt, G. C. Ho, G. M. Mason, M. A. Popecki, R. M. Skoug, C. W. Smith, E. C. Stone, and T. H. Zurbuchen, “STEREO and ACE: Coordinated Science”, invited talk (20 min) presented at the 35^th COSPAR Scientific Assembly, Paris, France, 18-25 July 2004, Paper E2.1-0030-04.

 

41.     Mason, G. M., M. I. Desai, J. E. Mazur, and J. R. Dwyer, “Remnant flare suprathermals and the seed population for shock-accelerated energetic particles”, invited plenary talk (30 min) presented at the AGU Chapman Conference on Solar Energetic Particles and Plasmas, Turku, Finland, Aug. 2-6, 2004.

 

42.     Mewaldt, R. A., C. M. S. Cohen, and G. M. Mason, “The source material for large solar energetic particle events”, invited talk (20 min) presented at the AGU Chapman Conference on Solar Energetic Particles and Plasmas, Turku, Finland, Aug. 2-6, 2004.  (see also publication list)

 

43.     Desai, M. I., G. M. Mason, J. R. Dwyer, J. E. Mazur, R. E. Gold, S. M. Krimigis, R. M. Skoug, C. W. Smith, C. M. S. Cohen, and M. E. Wiedenbeck, “ACE observations of SEPs during solar cycle 23: Implications for SEP acceleration models”, Invited Talk (30 min.), presented at the Huntsville 2004 Workshop: Challenges to Modeling the Sun-Earth System, Huntsville, Alabama, Oct. 18-22, 2004.

 

44.     Mason, G. M., “Space Weather from Explosive Events at the Sun”, Invited Union Tutorial, 60 min., EOS, Trans. AGU, 85(47), Fall Meet. Suppl., Abstract U11A-02.

 

45.     Mewaldt, R. A., C. M. S. Cohen, A. W. Labrador, R. A. Leske, E. C. Stone, G. M. Mason, M. I. Desai, M. L. Looper, R. S. Selesnick, J. E. Mazur, and D. K. Haggerty, “Spectra and energy content of ions accelerated in large solar particle events”, Invited paper, presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

46.     Desai, M. I., G. M. Mason, J. E. Mazur, and J. R. Dwyer, “Properties of the suprathermal seed population for interplanetary shocks near 1 AU”, Invited paper, presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

47.     Mazur, J. E., G. M. Mason, M. Popecki, and B. Klecker, “Solar particle charge states as clues to shock processes”, Invited paper, (20 min.) presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

48.     Lario, D., G. C. Ho, Q. Hu, R. B. Decker, M. I. Desai, and C. W. Smith, “Associations between interplanetary transient shock parameters and >47 keV ion intensity histories”, Invited paper, (20 min.) presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

49.     Mason, G. M., M. I. Desai, J. E. Mazur, and J. R. Dwyer, “What material is accelerated by interplanetary shocks?”, Invited paper, presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

50.     Mewaldt, R. A., C. M. S. Cohen, A. W. Labrador, R. A. Leske, E. C. Stone, G. M. Mason, M. I. Desai, M. R. Looper, R. S. Selesnick, J. E. Mazur, D. K. Haggerty, M. E. Wiedenbeck, and T. T. von Rosenvinge, “Spectra and energy content of ions accelerated in large solar particle events”, Invited paper, (20 min.) presented at: 4^th Annual International IGPP-UCRiverside Astrophysics Conference, The Physics of Collisionless Shocks, Palm Springs, CA, Feb 26-March 3, 2005.

 

51.     Desai, M. I., G. M. Mason, J. E. Mazur, J. R. Dwyer, and T. T. von Rosenvinge, “The source population for upstream ion events near the Earth’s bow shock”, Invited paper (15 min), presented at the European Geosciences Union, Vienna, Austria, April 24-29, 2005, Geophysical Research Abstracts, 7, 02925, 2005.

 

52.     Channok, C., D. Ruffolo, M. I. Desai, and G. M. Mason, “Finite time shock acceleration and fits to ESP ion spectra”, invited talk (20 min.) presented at the NSF/SHINE 2005 meeting, Kailua-Kona, Hawaii, July 10-15, 2005.

 

53.     Mason, G. M., “Solar energetic particle acceleration -- recent progress and current issues”, invited talk (25 min.) presented at the STER