J/ApJ/908/5 421 Forbush Decreases with 1995/2015 EPHIN/SOHO (Belov+, 2021)
On the Rigidity Spectrum of Cosmic-Ray Variations within Propagating
Interplanetary Disturbances: Neutron Monitor and SOHO/EPHIN Observations at
∼1-10GV.
Belov A., Papaioannou A., Abunina M., Dumbovic M., Richardson I.G.,
Heber B., Kuhl P., Herbst K., Anastasiadis A., Vourlidas A., Eroshenko E.,
Abunin A.
<Astrophys. J., 908, 5 (2021)>
=2021ApJ...908....5B 2021ApJ...908....5B
ADC_Keywords: Solar system; Sun
Keywords: Solar coronal mass ejections ; Forbush effect ; Corotating
streams
Abstract:
The rigidity dependence of all Forbush Decreases (FDs) recorded from
1995 to 2015 has been determined using neutron monitor (NM) and Solar
and Heliospheric Observatory (SOHO) (EPHIN) spacecraft data, covering
the energy (rigidity) range from ∼433MeV (1GV) to 9.10GeV (10GV). We
analyzed a total of 421 events and determined the spectrum in rigidity
with an inverse power-law fit. As a result, the mean spectral index
was identified to be <γF≥0.46±0.02. The majority (∼66%) of
the FDs have γF within the range 0.3-0.7. The remaining
one-third of the events (∼33%) have either (very) soft or hard FD
spectra, with the latter being more common than the former.
Significant variations of γF occur within almost every FD event.
During the initial FD decay phase the spectrum becomes gradually
harder, in contrast to the recovery phase, when it becomes softer.
Additionally, low energies (rigidities) seem to be better suited for
studying the fine structure of interplanetary disturbances (primarily
interplanetary coronal mass ejections) that lead to FDs. In
particular, FDs recorded by the EPHIN instrument on SOHO better
capture a two-step structure than FDs observed by NMs. Finally, the
ejecta of an ICME, especially when identified as a magnetic cloud,
often leads to abrupt changes in the slope of γF.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 57 421 The list of Forbush Decreases recorded at EPHIN
onboard SOHO from 1995 to 2015
--------------------------------------------------------------------------------
See also:
J/ApJ/896/133 : 2001-2019 ICME associate Forbush decrease events (Light+, 2020)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- NumID [1/421] Event number
6- 9 I4 yr Date.Y [1995/2015] Event date; year
11- 12 I2 "month" Date.M Event date; month
14- 15 I2 d Date.D Event date; day
17- 21 A5 --- Time Forbush decrease onset time; hh:mm
23- 27 F5.2 % AS [0.6/16.8] Forbush decrease amplitude by EPHIN
29- 31 F3.1 % AE [0.3/9] Forbush decrease magnitude by neutron
monitors
33- 37 F5.2 --- gammaF [-0.68/1.26] Mean spectral index
39- 42 F4.2 --- e_gammaF [0.03/0.7] Uncertainty in gammaF
44- 52 A9 --- Type Structure type; Corotating Interaction Regions
and/or Interplanetary Coronal Mass Ejections
54- 54 I1 --- EPHIN [0/1] A two-step Forbush decrease from EPHIN?
0=No, 1=Yes
56- 57 I2 --- NMs [0/1] A two-step Forbush decrease from NMs?
0=No, 1=Yes
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 22-Jun-2022