89 research outputs found
Variations of geomagnetic cutoff rigidities during the series of geomagnetic storms in January 2005: observations and modelling
Coupling functions for lead and lead-free neutron monitors from the latitudinal measurements performed in 1982 in the research station Academician Kurchatov
The latitudinal behavior of intensities and multiplicities was registered by the neutron monitor 2 NM and the lead-free neutron monitor 3 SND (slow-neuron detector) in the equator-Kaliningrad line in the Atlantic Ocean. Coupling coefficients for 3 SND show the sensitivity of this detector to primary particles of cosmic rays of energies on the average lower than for 2 NM. As multiplicities increase, the coupling coefficients shift towards higher energies
Ground increase of cosmic ray intensity on February 16, 1984
The event of February 16, 1984 is one of the two largest ground increases of solar cosmic rays (CR) in the last two cycles of solar activity. This event happended at a decrease of the 21-st cycle against a quiet background. Although at the beginning of 1984 the observed indices of solar activity were higher than those at the end of 1983, the day of February 16 16 may be characterized as very quiet. On that day the geomagnetic perturbance (Sigma F sub p = 14, A sub p = 7) was the lowest in February. After a small Forbush decrease due to the magnetic storm of February 12-13, the CR intensity almost completely recovered by February 16. Thus, the solar particles that came to the Earth on February 16 got into a practically unperturbed magnetosphere, and the variations of secondary CR induced by these particles were not superimposed on any other substantial variations of extraterrestrial or magnetospheric origin
About long term modulation of cosmic rays in the 23-24 solar activity cycles
Recently, there has been a significant trend in magnetic fields on the Sun. The total magnetic field of the Sun
from the end of the 22nd cycle of solar activity (SA) has more than halved and this decrease continues. Chan-
ges in the magnetic field are the key to all the active phenomena occurring on the Sun and in the heliosphere
and, accordingly, to processes in cosmic rays. In long-term CR variations in 23-24 cycles of SA the attenuation
of the solar magnetic field is displayed and these variations turned out to be the smallest for the entire time of
CR observations. Model calculations of CR modulation for 21-22 and 23-24 cycles of SA showed: with a slight
difference in the regression characteristics obtained, the distribution of contributions to the generated CR
modulation from the effects of various SA indices is strongly varies in the analyzed periods. Possible reasons
for the features of the last two CA cycles are discussed
Relationship of the characteristics of large Forbush decreases and the heliolongitude of their sources
In this investigation the different features and characteristics of Forbush decreases, with emphasis on large For-
bush decreases (â„4%) and their association to solar sources, are being examined. According to the heliolongitude
of the solar source, the events under study were separated into three subcategories: western (21Âș †heliolongitude
†60Âș), eastern (-60Âș †heliolongitude †-21Âș) and central (-20Âș †heliolongitude †20Âș). The selected events cover
the time period 1967 - 2017. The âGlobal Survey Methodâ was used for analyzing the Forbush decreases, along with
data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst), and interplanetary magnetic field. In ad -
dition, the superimposed epoch method was applied in order to plot the time profiles for the aforementioned group
of events. This detailed analysis reveals interesting results concerning the features of cosmic ray decreases in re-
gard to the heliolongitude of the solar sources. Moreover, it is also shown that large Forbush decreases, regardless
of the heliolongitude of the solar source, are accompanied by increased geomagnetic activity and increased aniso-
tropy, including anisotropy before the events, which can serve as a typical precursor of Forbush decreases
Unusual decrease of the cosmic ray intensity in May 2019 on the background of the minima solar activity
In May 2019 there was a long and sloping decreasing of cosmic rayâs intensity (up to ~4%), which was observed
on neutron monitors. Despite this was a small decreasing compared to quasi-eleven-period variation, it stands
out well in 24th cycle of solar activity.
According to LASCO/SOHO and STEREO-A data from spectrometer in different UHF bands and from coronograph,
there was a series of CMEs which affected on modulation of cosmic rays by creating a series of Forbush decrea -
sing, which didnât restore. This series was connected to two active regions on sun and began on April 30 from
âreversed haloâ CME. This CME didnât reach the earth, but led to significant additional modulation of cosmic rays,
mostly on east side. Later there was a series of smaller CMEs on May 1-6, which also didnât reach the earth, but
were gradually approaching to Earth. Recent CMEs on 8-9 and 12-13 created a normal Forbush decreasing.
In May 2019, cosmic rays shown again, that they can collect information about distant objects of geliosphere and
transmit it to Earth. The ground-level detectors sometimes can observe an interaction of interplanetary distur-
bances, which didnât reach the earth. East CMEs are especially effective, because they closing magnetic field
lines beyond the orbit of earth and can interfere the restoring of cosmic rayâs intensity
Snow effect on the neutron monitor network for 2018-2019
In this article, the influence of the surrounding snow cover on the neutron monitors count rate of the world network of neutron monitors was estimated using the method of reference stations. The applied technique also makes it possible to estimate the snow cover thickness at the observation point, which was done for more than two dozen stations. A comparison of the data correction results for snow is carried out for the case of automatic correction, based on the developed algorithm, and for manual one, with an error estimate
The new Athens center on data processing from the neutron monitor network in real time
International audienceThe ground-based neutron monitors (NMs) record galactic and solar relativistic cosmic rays which can play a useful key role in space weather forecasting, as a result of their interaction with interplanetary disturbances. The Earth's-based neutron monitor network has been used in order to produce a real-time prediction of space weather phenomena. Therefore, the Athens Neutron Monitor Data Processing Center (ANMODAP) takes advantage of this unique multi-directional device to solve problems concerning the diagnosis and forecasting of space weather. At this moment there has been a multi-sided use of neutron monitors. On the one hand, a preliminary alert for ground level enhancements (GLEs) may be provided due to relativistic solar particles and can be registered around 20 to 30 min before the arrival of the main part of lower energy particles responsible for radiation hazard. To make a more reliable prognosis of these events, real time data from channels of lower energy particles and X-ray intensity from the GOES satellite are involved in the analysis. The other possibility is to search in real time for predictors of geomagnetic storms when they occur simultaneously with Forbush effects, using hourly, on-line accessible neutron monitor data from the worldwide network and applying a special method of processing. This chance of prognosis is only being elaborated and considered here as one of the possible uses of the Neutron Monitor Network for forecasting the arrival of interplanetary disturbance to the Earth. The achievements, the processes and the future results, are discussed in this work
COSMIC-RAY VARIATIONS DURING THE TWO GREATEST BURSTS OF SOLAR ACTIVITY IN THE 23RD SOLAR CYCLE
Abstract. During two extreme bursts of solar activity in March-April 2001 and October-November 2003, the ground-based neutron monitor network recorded a series of outstanding events distinguished by their magnitude and unusual peculiarities. The important changes that lead to increased activity initiated not with the sunspot appearance, but with the large-scale solar magnetic field reconfiguration. A series of strong and moderate magnetic storms and powerful proton events (including ground-level enhancements, GLE) were registered during these periods. The largest and most productive in the 23rd solar cycle, active region 486, generated a significant series of solar flares among which the 4 November 2003 flare (X28/3B) was the most powerful X-ray solar event ever observed. The fastest arrival of the interplanetary disturbance from the Sun (after August 1972) and the highest solar wind velocity and IMF intensity were recorded during these events. Within 1 week, three GLEs of solar cosmic rays were registered by the neutron monitor network (28 and 29 October and 2 November 2003). In this work, we perform a tentative analysis of a number of the effects seen in cosmic rays during these two periods, using the neutron monitor network and other relevant data
Space weather and space anomalies
A large database of anomalies, registered by 220 satellites in different orbits over the period 1971-1994 has been compiled. For the first time, data from 49 Russian Kosmos satellites have been included in a statistical analysis. The database also contains a large set of daily and hourly space weather parameters. A series of statistical analyses made it possible to quantify, for different satellite orbits, space weather conditions on the days characterized by anomaly occurrences. In particular, very intense fluxes (>1000 pfu at energy >10 MeV) of solar protons are linked to anomalies registered by satellites in high-altitude (>15000 km), near-polar (inclination >55°) orbits typical for navigation satellites, such as those used in the GPS network, NAVSTAR, etc. (the rate of anomalies increases by a factor ~20), and to a much smaller extent to anomalies in geostationary orbits, (they increase by a factor ~4). Direct and indirect connections between anomaly occurrence and geomagnetic perturbations are also discussed
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