Geomagnetic activity and diurnal variation of cosmic ray neutron intensity

1965 ◽  
Vol 62 (3) ◽  
pp. 139-144
Author(s):  
D. S. R. Murty ◽  
Y. Nagabhushanam ◽  
K. Ramanuja Rao
Keyword(s):  
Diurnal Variation ◽  
Geomagnetic Activity ◽  
Cosmic Ray ◽  
Neutron Intensity

Time and other Variations in the Intensity of Cosmic Ray Neutrons

1951 ◽  
Vol 6 (11) ◽  
pp. 592-598
Author(s):  
N. Adams ◽  
H. J. J. Braddick
Keyword(s):  
Cosmic Rays ◽  
Solar Flare ◽  
Diurnal Variation ◽  
Sea Level ◽  
Geomagnetic Latitude ◽  
Cosmic Ray ◽  
Temporal Variations ◽  
Neutron Production ◽  
Neutron Intensity

AbstractWe have measured the barometer coefficient of cosmic ray neutron production at sea level and find the value -9,25% ± 0,20/cmHg. We have shown that there is no diurnal variation of neutron production of amplitude greater than about 0,4 %. The effects of the large solar flare of November 19 th , 1949 on cosmic ray neutrons were much greater than on ionising cosmic rays at sea level; the maximum factor of increase was more than 5 and the intensity remained measurably above normal for about 12 hours. A small increase of neutron intensity is found, statistically, to be correlated with a number of recorded radio fade-outs. It is suggested that neutron measurements are particularly suitable for studying temporal variations of cosmic rays. The latitude increase of cosmic ray neutrons between geomagnetic latitude 54,5° and 56,5° was found to be about 2%. No certain increase was found between 56,5° and 59,5°.

Solar Magnetic Moment and Diurnal Variation in Cosmic-Ray Intensity

1954 ◽  
Vol 93 (3) ◽  
pp. 551-553 ◽  
Author(s):  
J. Firor ◽  
F. Jory ◽  
S. B. Treiman
Keyword(s):  
Diurnal Variation ◽  
Magnetic Moment ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity

Characteristics of enhanced and low-amplitude cosmic-ray diurnal variation

Solar Physics ◽  
1995 ◽  
Vol 159 (1) ◽  
pp. 191-202 ◽  
Author(s):  
A. G. Ananth ◽  
K. Kudela ◽  
D. Venkatesan
Keyword(s):  
Diurnal Variation ◽  
Cosmic Ray ◽  
Low Amplitude

scholarly journals Variability of Weddell Sea ionospheric anomaly as deduced from observations at the Akademik Vernadsky station

2021 ◽  
pp. 47-55
Author(s):  
A. Zalizovski ◽  
◽  
I. Stanislawska ◽  
V. Lisachenko ◽  
O. Charkina ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Electron Density ◽  
Geomagnetic Activity ◽  
Dynamic Equilibrium ◽  
Doppler Frequency ◽  
Weddell Sea ◽  
K Index ◽  
Weddell Sea Anomaly ◽  
Index Level ◽  
Solar Ultraviolet

Ionospheric Weddell Sea anomaly is an inversion of diurnal variation of the electron density in the ionosphere over Antarctic Peninsula, Weddell Sea, and neighbor territories observed during Antarctic summer. This paper aims at analyzing the reaction of the ionosphere during the Weddell Sea anomaly to changes in solar and geomagnetic activity as deduced from the data of vertical sounding of the ionosphere conducted at the Akademik Vernadsky station. The aim is achieved by comparing the monthly median values of the critical frequencies of the ionosphere (foF2) during Weddell Sea anomaly for the years of high and low solar activity; as well as by comparison of median December height-time diagrams (HT-diagrams) of foF2 calculated separately for the time intervals characterized by low or high levels of F10.7 and K indices for the period from 2007 till 2016. It was experimentally demonstrated that the Weddell Sea anomaly depends on the levels of solar ultraviolet flux and local K indices. The biggest nighttime maximum of ionization corresponds to low K indices and high values of F10.7. The most accurate inversion of diurnal variation of electron density in the F region is observed under the low values of K index and low F10.7 flux. The growth of geomagnetic activity decreases the nighttime ionization under both low and high levels of F10.7 fluxes and leads to a blur of the night maximum. Visible virtual heights of maximums increase together with F10.7 independently of the K index level. Blurring of the night maximum can be explained by destruction of the field of thermospheric winds supporting the nighttime anomaly, and/or by increasing role of plasma drifts in comparison with wind impact. The growth of visible virtual height of the nighttime maximum with increasing solar F10.7 flux could be explained by the gain of equatorward thermospheric wind with increasing solar ultraviolet flux that leads to growth of plasma upwelling effect. The Doppler frequency shift of the signals reflected from the ionosphere during nighttime in presence of the Weddell Sea anomaly is close to zero which could be explained by a stable F2 layer formed as a result of dynamic equilibrium between photochemical processes and upward plasma transport.

Cosmic Ray Radiation Effects on Space Environment Associated to Intense Solar and Geomagnetic Activity

2007 ◽  
Vol 54 (4) ◽  
pp. 1089-1096 ◽  
Author(s):  
H. Mavromichalaki ◽  
A. Papaioannou ◽  
G. Mariatos ◽  
M. Papailiou ◽  
A. Belov ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Radiation Effects ◽  
Cosmic Ray ◽  
Space Environment

A reevaluation of the atmospheric pressure dependence of secondary cosmic-ray neutrons in the context of Cosmic-Ray Neutron Sensing

2021 ◽  
Author(s):  
Jannis Weimar ◽  
Paul Schattan ◽  
Martin Schrön ◽  
Markus Köhli ◽  
Rebecca Gugerli ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Hydrogen Content ◽  
Atmospheric Pressure ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Atmospheric Air ◽  
Neutron Intensity ◽  
The Earth ◽  
Wide Range ◽  
Primary Cosmic Rays

<p><span>Secondary cosmic-ray neutrons may be effectively used as a proxy for environmental hydrogen content at the hectare scale. These neutrons are generated mostly in the upper layers of the atmosphere within particle showers induced by galactic cosmic rays and other secondary particles. Below 15 km altitude their intensity declines as primary cosmic rays become less abundant and the generated neutrons are attenuated by the atmospheric air. At the earth surface, the intensity of secondary cosmic-ray neutrons heavily depends on their attenuation within the atmosphere, i.e. the amount of air the neutrons and their precursors pass through. Local atmospheric pressure measurements present an effective means to account for the varying neutron attenuation potential of the atmospheric air column above the neutron sensor. Pressure variations possess the second largest impact on the above-ground epithermal neutron intensity. Thus, using epithermal neutrons to infer environmental hydrogen content requires precise knowledge on how to correct for atmospheric pressure changes.</span></p><p><span>We conducted several short-term field experiments in saturated environments and at different altitudes, i.e. different pressure states to observe the neutron intensity pressure relation over a wide range of pressure values. Moreover, we used long-term measurements above glaciers in order to monitor the local dependence of neutron intensities and pressure in a pressure range typically found in Cosmic-Ray Neutron Sensing. The results are presented along with a broad Monte Carlo simulation campaign using MCNP 6. In these simulations, primary cosmic rays are released above the earth atmosphere at different cut-off rigidities capturing the whole evolution of cosmic-ray neutrons from generation to attenuation and annihilation. The simulated and experimentally derived pressure relation of cosmic-ray neutrons is compared to those of similar studies and assessed in the light of an appropriate atmospheric pressure correction for Cosmic-Ray Neutron Sensing.</span></p>

scholarly journals Investigating temporal field sampling strategies for site-specific calibration of three soil moisture–neutron intensity parameterisation methods

2015 ◽  
Vol 19 (7) ◽  
pp. 3203-3216 ◽  
Author(s):  
J. Iwema ◽  
R. Rosolem ◽  
R. Baatz ◽  
T. Wagener ◽  
H. R. Bogena
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Satellite Remote Sensing ◽  
Cosmic Ray ◽  
Sampling Strategies ◽  
Site Specific ◽  
Neutron Intensity ◽  
Soil Wetness ◽  
Semi Arid

Abstract. The Cosmic-Ray Neutron Sensor (CRNS) can provide soil moisture information at scales relevant to hydrometeorological modelling applications. Site-specific calibration is needed to translate CRNS neutron intensities into sensor footprint average soil moisture contents. We investigated temporal sampling strategies for calibration of three CRNS parameterisations (modified N0, HMF, and COSMIC) by assessing the effects of the number of sampling days and soil wetness conditions on the performance of the calibration results while investigating actual neutron intensity measurements, for three sites with distinct climate and land use: a semi-arid site, a temperate grassland, and a temperate forest. When calibrated with 1 year of data, both COSMIC and the modified N0 method performed better than HMF. The performance of COSMIC was remarkably good at the semi-arid site in the USA, while the N0mod performed best at the two temperate sites in Germany. The successful performance of COSMIC at all three sites can be attributed to the benefits of explicitly resolving individual soil layers (which is not accounted for in the other two parameterisations). To better calibrate these parameterisations, we recommend in situ soil sampled to be collected on more than a single day. However, little improvement is observed for sampling on more than 6 days. At the semi-arid site, the N0mod method was calibrated better under site-specific average wetness conditions, whereas HMF and COSMIC were calibrated better under drier conditions. Average soil wetness condition gave better calibration results at the two humid sites. The calibration results for the HMF method were better when calibrated with combinations of days with similar soil wetness conditions, opposed to N0mod and COSMIC, which profited from using days with distinct wetness conditions. Errors in actual neutron intensities were translated to average errors specifically to each site. At the semi-arid site, these errors were below the typical measurement uncertainties from in situ point-scale sensors and satellite remote sensing products. Nevertheless, at the two humid sites, reduction in uncertainty with increasing sampling days only reached typical errors associated with satellite remote sensing products. The outcomes of this study can be used by researchers as a CRNS calibration strategy guideline.

scholarly journals 36. The 27-day variation in cosmic ray intensity and in geomagnetic activity

1958 ◽  
Vol 6 ◽  
pp. 332-344 ◽  
Author(s):  
Scott E. Forbush
Keyword(s):  
Harmonic Analysis ◽  
Geomagnetic Activity ◽  
Statistical Significance ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Effective Number ◽  
Cosmic Ray Intensity ◽  
Fourth Group ◽  
Sunspot Minimum ◽  
Recurrence Tendency

The amplitude of the average 27-day wave in cosmic ray intensity, at Huancayo, Peru, and its phase relative to that for the 27-day wave in international magnetic character figure (ICF) is determined from results of harmonic analysis of data for each of 246 intervals (or solar rotations) of 27 days. From these data, the variability of which is essential for tests of statistical significance, the amplitude of the average 27-day wave in cosmic ray intensity and its phase relative to that in geomagnetic activity is determined for each of three groups of solar rotations selected according to the average of the amplitudes of the 27-day waves in magnetic activity. A fourth group contained only 27-day intervals in which large cosmic ray decreases occurred. Relative to that in magnetic activity, the phase of the 27-day wave in cosmic ray intensity is found for the averages, to be the same for the four groups.The maxima of the average cosmic ray waves occur about 1·5 days after the minima of the corresponding waves in ICF. In general, the amplitude of the average 27-day wave in cosmic ray intensity, in the co-ordinate system in which its phase is relative to that of the 27-day wave in ICF tends to be greater for the selected groups of rotations with larger average ICF amplitudes. For most years near sunspot minimum the amplitude of the 27-day cosmic ray wave does not differ significantly from zero.Bartels found for 27-day waves in ICF the effective number of statistically independent 27-day waves for N successive solar rotations to be N/3; the number found for cosmic ray intensity is N/2. Thus, on the average the 27-day recurrence tendency is less for cosmic ray intensity than for magnetic activity.

Seasonal and diurnal variations of geomagnetic activity and their role in Space Weather forecast

2001 ◽  
Vol 79 (6) ◽  
pp. 907-920 ◽  
Author(s):  
W Lyatsky ◽  
A M Hamza
Keyword(s):  
Solar Wind ◽  
Seasonal Variation ◽  
Diurnal Variation ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Weather Forecast ◽  
Diurnal Variations ◽  
Ionospheric Conductivity ◽  
Solar Wind Parameters ◽  
Possible Cause

A possible test for different models explaining the seasonal variation in geomagnetic activity is the diurnal variation. We computed diurnal variations both in the occurrence of large AE (auroral electrojet) indices and in the AO index. (AO is the auroral electrojet index that provides a measure of the equivalent zonal current.) Both methods show a similar diurnal variation in geomagnetic activity with a deep minimum around (3–7) UT (universal time) in winter and a shallower minimum near 5–9 UT in equinoctial months. The observed UT variation is consistent with the results of other scientists, but it is different from that expected from the Russell–McPherron mechanism proposed to explain the seasonal variation. It is suggested that the possible cause for the diurnal and seasonal variations may be variations in nightside ionospheric conductivity. Recent experimental results show an important role for ionospheric conductivity in particle acceleration and geomagnetic disturbance generation. They also show that low ionospheric conductivity is favorable to the generation of auroral and geomagnetic activity. The conductivity in conjugate nightside auroral zones (where substorm generation takes place) is minimum at equinoxes, when both auroral zones are in darkness. The low ionospheric conductivity at equinoxes may be a possible cause for the seasonal variation in the geomagnetic activity with maxima in equinoctial months. The diurnal variation in geomagnetic activity can be produced by the UT variation in the nightside ionospheric conductivity, which in winter and at equinoxes has a maximum around 4–5 UT that may lead to a minimum in geomagnetic activity at this time. We calculated the correlation patterns for the AE index versus solar-wind parameters inside and outside the (2–7) UT sector related to the minimum in geomagnetic activity. The correlation patterns appear different in these two sectors indeed, which is well consistent with the UT variation in geomagnetic activity. It also shows that it is possible to improve significantly the reliability of the Space Weather forecast by taking into account the dependence of geomagnetic activity not only on solar-wind parameters but also on UT and season. Our test shows that a simple account for the dependence of geomagnetic activity on UT can improve the reliability of the Space Weather forecast by at least 50% in the 2–7 UT sector in winter and equinoctial months. PACS No.: 91.25Le

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