Corotating Forbush Decreases

1968 ◽  
Vol 1 (4) ◽  
pp. 145-146 ◽  
Author(s):  
K. G. McCracken ◽  
I. Palmer
Keyword(s):  
Interplanetary Space ◽  
Forbush Decrease ◽  
Forbush Decreases ◽  
Particle Event

A natural introduction to this topic is a brief discussion of two phenomena observable in interplanetary space near Earth—the energetic storm particle event (ESPE), and the recurrent Forbush decrease.

A new model describing Forbush Decreases at Mars: combining the heliospheric modulation and the atmospheric influence

2020 ◽  
Author(s):  
Jingnan Guo ◽  
Robert Wimmer-Schweingruber ◽  
Mateja Dumbovic ◽  
Bernd Heber ◽  
Yuming Wang
Keyword(s):  
Interplanetary Space ◽  
Atmospheric Transport ◽  
Forbush Decrease ◽  
Martian Atmosphere ◽  
Galactic Cosmic Rays ◽  
Interplanetary Coronal Mass Ejections ◽  
Forbush Decreases ◽  
Mars Atmosphere ◽  
Interaction Regions ◽  
Energy Dependent

<p>Forbush decreases are depressions in the galactic cosmic rays (GCRs) which are mostly caused by the modulations of interplanetary coronal mass ejections (ICMEs) and also sometimes by stream/corotating interaction regions (SIRs/CIRs). Forbush decreases have been studied extensively using neutron monitors at Earth and have been recently, for the first time, measured on the surface of another planet - Mars by the Radiation Assessment Detector (RAD), on board Mars Science Laboratory’s (MSL) rover Curiosity. The modulation of the GCR particles by heliospheric transients in space is energy-dependent and afterwards these particles are also interacting with the Martian atmosphere with the interaction process depending on the particle type and energy. In order to study the space weather environment near Mars using the ground-measured Forbush decreases, it is important to understand and quantify the energy-dependent modulation of the GCR particles by not only the pass-by heliospheric disturbances but also the Martian atmosphere. In this study, we develop a model which combines the heliospheric modulation of GCRs and the atmospheric modification of such modulated GCR spectra to quantify the amplitudes of the Forbush decreases at Mars: both on ground and in the interplanetary space near Mars during the pass-by of an ICME/SIR. The modeled results are in good agreement when compared to studies of Forbush decreases caused by ICMEs/SIRs measured by MSL on the surface of Mars and by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft in orbit.  This supports the validity of both the Forbush decrease description and the Martian atmospheric transport models.  Our model can be potentially used to understand the property of ICMEs and SIRs passing Mars.</p>

The acceleration of energetic particle fluxes in shock fronts in interplanetary space

1968 ◽  
Vol 46 (10) ◽  
pp. S844-S848 ◽  
Author(s):  
U. R. Rao ◽  
K. G. McCracken ◽  
R. P. Bukata
Keyword(s):  
Particle Acceleration ◽  
Interplanetary Space ◽  
Forbush Decrease ◽  
Wave Model ◽  
Interplanetary Shocks ◽  
Forbush Decreases ◽  
Anisotropic Character ◽  
Particle Fluxes ◽  
Shock Wave Model ◽  
Shock Fronts

On six occasions during 1966, enhanced fluxes of > 7.5-MeV energetic particles have been observed coincident with the onset of a Forbush decrease which was initiated by a solar flare. The anisotropic character of the particle fluxes indicates that the particles were not trapped and that particle acceleration was occurring in the region associated with the onset of the Forbush decreases. Subsequent to the onset of the Forbush decreases, bidirectional anisotropies of 7.5–45 MeV-protons were observed. It will be shown that these observations provide strong evidence for the shock-wave model for the Forbush decrease. It is suggested that particle acceleration in interplanetary shocks is a commonly occurring phenomenon, and, in particular, it is suggested that recurrent ≈1-MeV proton events are due to particle acceleration in corotating shock fronts.

Utilizing galactic cosmic rays as signatures of coronal mass ejections

2021 ◽  
Author(s):  
Mateja Dumbovic
Keyword(s):  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Flux Rope ◽  
Forbush Decrease ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Forbush Decreases ◽  
Magnetic Structures ◽  
Different Types ◽  
Galactic Cosmic Ray

<p>Coronal mass ejections (CMEs) are the most violent eruptions in the solar system. They are one of the main drivers of the heliospheric variability and cause various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). In general, interplanetary magnetic structures interact with GCRs producing depressions in the GCR flux. Therefore, different types of interplanetary magnetic structures cause different types of GCR depressions, allowing us to distinguish between them. In the interplanetary space the CME typically consists of two structures: the presumably closed flux rope and the shock/sheath which is formed ahead of the flux rope as it propagates and expands in the interplanetary space. Interaction of GCRs with these two structures is modelled separately, where the flux-rope related Forbush decrease can be modelled assuming that the GCRs diffuse slowly into the expanding flux rope, which is initially empty at its center (ForbMod model). The resulting Forbush decrease at a given time, i.e. heliospheric distance, reflects the evolutionary properties of CMEs. However, ForbMod is not yet able to take into account complex, non-self-similar evolution of the flux rope. Nevertheless, Forbush decreases can undoubtedly give us information on the CMEs in the heliosphere, especially where other measurements are lacking, and with further development, Forbush decrease reverse modelling could provide insight into the CME evolution.</p>

Rigidity Dependence of Forbush Decreases

1992 ◽  
Vol 10 (1) ◽  
pp. 24-26 ◽  
Author(s):  
M. L. Duldig ◽  
J. E. Humble
Keyword(s):  
Energy Range ◽  
Neutron Monitor ◽  
Forbush Decrease ◽  
Forbush Decreases ◽  
Neutron Monitor Data ◽  
Monitor Data ◽  
Rigidity Dependence

AbstractIna recent paper, Lockwood et al. (1991) have used IMP spacecraft and Neutron Monitor data to consider the rigidity dependence of three large Forbush Decreases over the energy range 50 MeV to 30 GeV. Some of their conclusions are extrapolated to higher energies. In an earlier paper (Duldig, 1987a), one of us discussed the need to consider the presence of isotropic intensity waves when determining the Forbush Decrease spectrum at energies up to a few hundred GeV. Lockwood et al.’s conclusions are discussed in the light of these results.

Forbush decreases: Origin and development in the interplanetary space

1979 ◽  
Vol 2 (1) ◽  
pp. 1-52 ◽  
Author(s):  
N. Iucci ◽  
M. Parisi ◽  
M. Storini ◽  
G. Villoresi
Keyword(s):  
Interplanetary Space ◽  
Forbush Decreases

The effect of Forbush decreases on the polar-night HOx concentration

2021 ◽  
Author(s):  
Irina Mironova
Keyword(s):  
Forbush Decrease ◽  
Cosmic Ray ◽  
Solar Proton ◽  
Polar Night ◽  
Forbush Decreases ◽  
Ozone Loss ◽  
Solar Proton Events ◽  
Hydrogen Oxide ◽  
The Impact ◽  
Ionization Rates

<div> <div> <div> <p>It is well-known that energetic particle precipitations during solar proton events increase ionization rates in the middle atmosphere enhancing the production of hydrogen oxide radicals (HOx) involved in the catalytic ozone destruction cycle. There are many studies where the contribution of energetic particles to the formation of hydrogen oxide radicals and ozone loss has been widely investigated. However, until now, there was no solid evidence that the reduction in galactic cosmic ray fluxes during a magnetic storm, known as Forbush-effect, directly and noticeably affects the polar-night stratospheric chemistry.<br>Here, the impact of the Forbush decrease on the behaviour of hydrogen oxide radicals was explored using the chemistry-climate model SOCOL.<br>We found that hydrogen oxide radical lost about half of its concentration over the polar boreal night stratosphere owing to a reduction in ionization rates caused by Forbush decreases after solar proton events occurred on 17 and 20 of January 2005. A robust response in ozone was not found. There is not any statistically significant response in (NOx) on Forbush decrease events as well as over summertime in the southern polar region.<br>The results of this study can be used to increase the veracity of ozone loss estimation if stronger Forbush events can have a place.</p> <p>Reference: Mironova I, Karagodin-Doyennel A and Rozanov E (2021) , The effect of Forbush decreases on the polar-night HOx concentration affecting stratospheric ozone. Front. Earth Sci. 8:618583. doi: 10.3389/feart.2020.618583</p> <p>https://www.frontiersin.org/articles/10.3389/feart.2020.618583/full</p> <p>The study was supported by the Russian Science Foundation grant (RSF project No. 20-67-46016).</p> </div> </div> </div>

A comparison of the characteristics of corotating and flare-initiated Forbush decreases

1968 ◽  
Vol 46 (10) ◽  
pp. S994-S998 ◽  
Author(s):  
R. P. Bukata ◽  
K. G. McCracken ◽  
U. R. Rao
Keyword(s):  
Blast Wave ◽  
Time Scale ◽  
Forbush Decrease ◽  
Time Profile ◽  
Blast Waves ◽  
Time Structure ◽  
Deep Space ◽  
Forbush Decreases ◽  
Similarities And Differences ◽  
Shock Fronts

Data acquired by the deep space probes Pioneer VI and Pioneer VII which differ by [Formula: see text] in heliographic longitude are presented to illustrate the basic similarities and differences between the classes of Forbush decrease resulting from corotating shock fronts and radially propagating blast waves. An example is presented to establish directly the existence of the corotating Forbush decrease, and from the intensity–time profile of the event it is concluded that the detailed time structure of the Forbush decrease is invariant over a time scale of about 4 days. An example of the Forbush decrease resulting from a solar-induced blast wave is also presented wherein an azimuthal gradient of about a factor of 4 per 60° of azimuth is observed.

Forbush decrease caused by interacting and non-interacting passing CME

2018 ◽  
Vol 13 (S340) ◽  
pp. 151-152
Author(s):  
Mohamed Ismaiel
Keyword(s):  
Solar Flares ◽  
Forbush Decrease ◽  
Forbush Decreases ◽  
Long Time ◽  
Short Time

AbstractOn 5-6 Aug. 2011 two short-time consecutive M-class solar flares led to profile of multiple Forbush Decreases showing the possible interaction of long-time passing of ICME.

scholarly journals 43. On the variations of the primary cosmic ray intensity

1958 ◽  
Vol 6 ◽  
pp. 420-427
Author(s):  
E. N. Parker
Keyword(s):  
Solar Activity ◽  
Interplanetary Space ◽  
Particle Density ◽  
Sunspot Cycle ◽  
Forbush Decrease ◽  
Cosmic Ray ◽  
Abrupt Onset ◽  
Cosmic Ray Intensity ◽  
Solar Origin ◽  
Quantitative Development

To construct a model for producing the observed variation in the cosmic ray intensity we consider primarily the Forbush decrease and the general decrease of the cosmic ray intensity during years of solar activity. These are larger variations than the diurnal and 27-day variations and require more drastic assumptions; thus they will better serve to establish a unique model.It is assumed that the sun does not emit cosmic ray particles except during the time of a solar flare. Thus, decreases in the cosmic ray intensity are to be interpreted as a solar effect which inhibits the arrival of galactic cosmic ray particles at earth. Since the intensity of low rigidity primary cosmic ray particles is observed to vary more than the intensity at higher rigidities, the inhibition has generally been assumed to be caused by magnetic fields.The necessary depression of the cosmic ray intensity requires both a barrier, to impede their arrival, and a removal mechanism within the barrier, to prevent eventual statistical equilibrium (with uniform particle density). Quantitative development indicates that a heliocentric magnetic dipole, a heliocentric cavity in the galactic field (Davis, Phys. Rev.100, 1440, 1955), and a heliocentric interplanetary cloud barrier (Morrison, Phys. Rev.101, 1397, 1956) all encounter serious difficulties in explaining the observed effects, one reason being the ineffective removal that is available.It is shown that a geocentric magnetic cloud barrier does not encounter these difficulties: it is proposed that during the years of solar activity the terrestrial gravitational field captures magnetic gas of solar origin from interplanetary space, which is then supported by the geomagnetic field; the removal by absorption by the earth is sufficiently effective that only a relatively thin barrier need be maintained; the occasional capture of new magnetic material accounts for the abrupt onset of the Forbush decreases, and the slow decay (0·5 years) of the captured fields for the smooth variation of the mean cosmic ray intensity with the sunspot cycle.

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