North-south anisotropy and radial density gradient of galactic cosmic rays.

Yasue, S.

doi:10.5636/jgg.32.617

Cited by 26 publications

(56 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They found no dependence of Gr on the polarity of the IMF in agreement with spacecraft observations and verified at higher rigidities (Yasue 1980, Swinson 1988), although Yasue found no significant variation in Gr from 1968 to 1972.…”

Section: Radial Density Gradientsupporting

confidence: 72%

“…This method of inferring the IMF sector was shown to be in about 75% agreement with spacecraft measurements of the sector type. Yasue (1980) derived the spectrum of r,Ts for the combined years 1968 to 1972. He found that the anisotropy was wealdy proportional to the rigidity of the particles (P 0-3) and that Pu was between 150 and 300 GV.…”

Section: Characteristics Of the Sidereal (North-south) Anisotropymentioning

confidence: 99%

“…Since the anisotropies are produced from solar modulation it is possible to derive solar parameters such as mean-free paths of particles and gradients in the number densities from observations of the anisotropies. For example, see the analyses by Yasue (1980) and Bieber and Chen (1991a).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Modulation of high‐energy cosmic rays in the heliosphere

Hall¹,

Humble²,

Duldig³

1994

J. Geophys. Res.

View full text Add to dashboard Cite

DECLARATIONSI certify that this thesis does not incorporate without acknowledgment any material previously submitted for a degree or diploma in any university; and to the best of my knowledge and belief it does not contain any material previously published or written by another person where due reference is not made in the text. Damian Lindsay Hallll This thesis may be made available for loan and limited copying in accordance with the Copyright Act 1968. Damian Lindsay Hall Ill ABSTRACTThe distribution of galactic cosmic ray particles in the heliosphere is influenced (modulated) by the Sun's interplanetary magnetic field (IMF) and the solar wind. The particles diffuse inward, convect outward and have drifts in the motion of their gyro-centres. They are also scattered from their gyro-orbits by irregularities in the IMF. These processes are the components of solar modulation and produce streaming (anisotropies) of particles in the heliosphere. The anisotropies can be investigated at Earth by examining the count rates of cosmic ray detectors. The anisotropic streams appear as diurnal and semi-diurnal variations in the count rates of cosmic ray recorders in solar and sidereal time. Theoretical models of solar modulation predict effects which are dependent on the polarity of the Sun's magnetic dipole (A >0 or A <0). The solar diurnal and North-South anisotropy can be used to test these predictions.The yearly averaged solar and sidereal diurnal variations in data recorded by seven neutron monitors and ten muon telescopes for the period 1957 to 1990 have been deduced by Fourier analysis methods. The rigidities of the galactic cosmic rays to which these instruments respond encompass the range 10 to 1400 Giga volts (GV). The rigidity spectrum of the solar diurnal anisotropy has been inferred to have a mean spectral index extremely close to zero and an idealised upper limiting rigidity of 100± 25 GV. This is in good agreement with previous determinations. It is shown that this upper limit has a temporal variation between 50 GV and 180 GV and is correlated with the magnitude of the IMF. The rigidity spectrum is likely to be dependent on the polarity of the Sun's magnetic dipole, the spectral index being determined as positive in the A >0 magnetic polarity state and negative in the A <0 polarity state. It is also shown that the amplitude of the anisotropy varies with an 11-year variation and the time of maximum varies with 22-year variation. Both of these variations are shown to be independent of any change in the rigidity spectrum.The solar diurnal anisotropy is also used as a tool to calculate the modulation parameters ?Lip, (the product of the parallel mean-free path and radial density gradient) and Gtzl (an indicator of the symmetric latitudinal density gradient). X G r is found to have a 22-year II variation at all rigidities studied and furthermore to only have rigidity dependence when the heliosphere is in the A >0 magnetic polarity state. It is unlikely that X IIG r has any rigidity dependence in the A <0 polarity s...

show abstract

Section: Radial Density Gradientsupporting

confidence: 72%

Section: Characteristics Of the Sidereal (North-south) Anisotropymentioning

confidence: 99%

See 1 more Smart Citation

Modulation of high‐energy cosmic rays in the heliosphere

Hall¹,

Humble²,

Duldig³

1994

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…Yasue (1980) analyzed the GG-component together with the sidereal diurnal variation observed by MDs and NMs and derived the power law-type rigidity spectrum of the average NS anisotropy with a positive power law index of approximately 0.3. By analyzing long-term variations of the 3D anisotropies observed with Nagoya MD and NMs on yearly basis, Munakata et al (2014) confirmed that the perpendicular component including the NS anisotropy increases with GCR rigidity.…”

Section: Summary and Discussionmentioning

confidence: 99%

The spatial density gradient of galactic cosmic rays and its solar cycle variation observed with the Global Muon Detector Network

et al. 2014

View full text Add to dashboard Cite

We derive the long-term variation of the three-dimensional (3D) anisotropy of approximately 60 GV galactic cosmic rays (GCRs) from the data observed with the Global Muon Detector Network (GMDN) on an hourly basis and compare it with the variation deduced from a conventional analysis of the data recorded by a single muon detector at Nagoya in Japan. The conventional analysis uses a north-south (NS) component responsive to slightly higher rigidity (approximately 80 GV) GCRs and an ecliptic component responsive to the same rigidity as the GMDN. In contrast, the GMDN provides all components at the same rigidity simultaneously. It is confirmed that the temporal variations of the 3D anisotropy vectors including the NS component derived from two analyses are fairly consistent with each other as far as the yearly mean value is concerned. We particularly compare the NS anisotropies deduced from two analyses statistically by analyzing the distributions of the NS anisotropy on hourly and daily bases. It is found that the hourly mean NS anisotropy observed by Nagoya shows a larger spread than the daily mean due to the local time-dependent contribution from the ecliptic anisotropy. The NS anisotropy derived from the GMDN, on the other hand, shows similar distribution on both the daily and hourly bases, indicating that the NS anisotropy is successfully observed by the GMDN, free from the contribution of the ecliptic anisotropy. By analyzing the NS anisotropy deduced from neutron monitor (NM) data responding to lower rigidity (approximately 17 GV) GCRs, we qualitatively confirm the rigidity dependence of the NS anisotropy in which the GMDN has an intermediate rigidity response between NMs and Nagoya. From the 3D anisotropy vector (corrected for the solar wind convection and the Compton-Getting effect arising from the Earth's orbital motion around the Sun), we deduce the variation of each modulation parameter, i.e., the radial and latitudinal density gradients and the parallel mean free path for the pitch angle scattering of GCRs in the turbulent interplanetary magnetic field. We show the derived density gradient and mean free path varying with the solar activity and magnetic cycles.

show abstract

“…The ecliptic component has been derived from the amplitude and phase of the solar diurnal anisotropy in many papers [4,5,6], while the north-south anisotropy (NSA) parallel to the Earth's rotation axis has been derived from NM and MD data in a couple of different ways [7,8,9]. Mori and Nagashima (1979) [10] proposed a way to derive the NSA from the "GG-component" of a single multi-directional MD at Nagoya in Japan.…”

Section: Introductionmentioning

confidence: 99%

North-south anisotropy of galactic cosmic rays observed with the Global Muon Detector Network (GMDN)

Munakata¹

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

View full text Add to dashboard Cite

We analyze the north-south anisotropy (NSA) of galactic cosmic rays observed with the GMDN on an hourly basis and compare with the anisotropy derived from the GG-component of a large multidirectional muon detector at Nagoya, Japan. The NSA is a component of the three dimensional anisotropy vector parallel to the Earth's rotation axis. We find a significant seasonal variation of the NSA from the GG-component indicating the influence of the anisotropy component in the ecliptic plane to the NSA. We calculate the average and standard deviation of daily mean NSAs in the "toward" (T) and "away" (A) IMF sectors separately in each Carrington Rotation between December 1993 and November 2014. It is confirmed that the temporal variations of the NSA observed with the GMDN and GG-component are consistent with each other, as reported earlier. We find the T-A separation between average NSAs in T and A sectors shows a long-term variation with minima (maxima) around the solar activity minima (maxima). The standard deviation in each rotation also shows a similar long-term variation, keeping the ratio of T-A separation to the standard deviation roughly constant thorough out an entire period of analysis. We discuss this in relation with the "success rate" which is introduced as a parameter indicating to what extent we can infer the IMF sector polarity from the sign of the observed NSA.

show abstract

North-south anisotropy and radial density gradient of galactic cosmic rays.

Cited by 26 publications

References 11 publications

Modulation of high‐energy cosmic rays in the heliosphere

Modulation of high‐energy cosmic rays in the heliosphere

The spatial density gradient of galactic cosmic rays and its solar cycle variation observed with the Global Muon Detector Network

North-south anisotropy of galactic cosmic rays observed with the Global Muon Detector Network (GMDN)

Contact Info

Product

Resources

About