Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance

K. Kecskeméty, E. I. Daibog, Yu I. Logachev, J. Kóta, R. A. Mewaldt

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

The shape of the particle flux decline in solar energetic particle (SEP) events is of particular importance in understanding the propagation of energetic particles in the interplanetary medium. The majority of few-MeV particle events exhibit exponential declines indicating the importance of adiabatic deceleration and convection transport. Then value of the decay time τ depends on the differential spectral index γ, solar wind speed, and on the distance from the Sun. By analyzing the dependence of τ on environmental plasma parameters we showed earlier that τ tends to decrease with the increase of both solar wind speed and magnetic field strength. Comparing simultaneous observations at various radial distances (at IMP, ACE, Helios, and Ulysses) we find that whereas high-energy (tens of MeVs) proton profiles sometimes are surprisingly identical at different radii, MeV protons in the same events have significantly longer decays at farther locations than near 1 AU. This is incompatible both with pure diffusive particle propagation and with trapping between converging magnetic field lines near the Sun and at the front of traveling shock, but qualitatively supports convection transport and adiabatic deceleration. Using a simple numerical model including diffusion and adiabatic cooling the time profiles are calculated and compared with observations.

Original languageEnglish
Title of host publication29th International Cosmic Ray Conference, ICRC 2005
PublisherTata Institute of Fundamental Research
Pages343-346
Number of pages4
Volume1
Publication statusPublished - 2005
Event29th International Cosmic Ray Conference, ICRC 2005 - Pune, India
Duration: Aug 3 2005Aug 10 2005

Other

Other29th International Cosmic Ray Conference, ICRC 2005
CountryIndia
CityPune
Period8/3/058/10/05

Fingerprint

interplanetary medium
energetic particles
decay rates
deceleration
solar wind
sun
convection
IMP
protons
propagation
decay
profiles
flux (rate)
magnetic fields
field strength
shock
trapping
cooling
radii
energy

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Kecskeméty, K., Daibog, E. I., Logachev, Y. I., Kóta, J., & Mewaldt, R. A. (2005). Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance. In 29th International Cosmic Ray Conference, ICRC 2005 (Vol. 1, pp. 343-346). Tata Institute of Fundamental Research.

Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance. / Kecskeméty, K.; Daibog, E. I.; Logachev, Yu I.; Kóta, J.; Mewaldt, R. A.

29th International Cosmic Ray Conference, ICRC 2005. Vol. 1 Tata Institute of Fundamental Research, 2005. p. 343-346.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Kecskeméty, K, Daibog, EI, Logachev, YI, Kóta, J & Mewaldt, RA 2005, Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance. in 29th International Cosmic Ray Conference, ICRC 2005. vol. 1, Tata Institute of Fundamental Research, pp. 343-346, 29th International Cosmic Ray Conference, ICRC 2005, Pune, India, 8/3/05.
Kecskeméty K, Daibog EI, Logachev YI, Kóta J, Mewaldt RA. Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance. In 29th International Cosmic Ray Conference, ICRC 2005. Vol. 1. Tata Institute of Fundamental Research. 2005. p. 343-346
Kecskeméty, K. ; Daibog, E. I. ; Logachev, Yu I. ; Kóta, J. ; Mewaldt, R. A. / Dependence of decay rates of SEP events on characteristics of interplanetary medium and on radial distance. 29th International Cosmic Ray Conference, ICRC 2005. Vol. 1 Tata Institute of Fundamental Research, 2005. pp. 343-346
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