scholarly journals The mean solar magnetic field as an indicator of the interplanetary magnetic field

1996 ◽  
Vol 39 (4) ◽  
Author(s):  
J. Bremer
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Structure Data ◽  
Solar Magnetic Field ◽  
Private Communication ◽  
Sector Structure ◽  
Ionospheric Effect ◽  
Ionospheric Response ◽  
The Earth ◽  
The Mean

The Mean Solar Magnetic Field (MSMF) measured daily by ground based observations at the Standford Observatory shows similar structures like the Interplanetary Magnetic Field (IMF) near the Earth about 5 to 7 days later. The ionospheric effect in the mid-latitude F2-region due to such MSMF changes is most marked for strong MSMF changes from anti to pro sectors. The mean ionospheric response is very similar to the results obtained earlier with IMF sector structure data derived from Svalgaard (1976) and Wilcox (1982, private communication). Therefore, the MSMF data can successfully be used to predict the mean IMF sector structure and the mean ionospheric response 5 to 7 days in advance.

scholarly journals Interplanetary magnetic field and its possible effects on the mid-latitude ionosphere II

1994 ◽  
Vol 37 (2) ◽  
Author(s):  
Y. Tulunay
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Interplanetary Magnetic Field ◽  
Sector Structure ◽  
Quiet Time ◽  
Time Value ◽  
The Mean ◽  
The Imf

Using criticaI frequencies, f0F2 from the Uppsala, Lannion and Dourbes ionosonde stations, the possible effects of the orientation of the IMF on mid-latitude ionosphere are further investigated. For this purpose, the regular diurnal, seasonal and solar cycle variations in the f0F2 data were removed by subtracting the mean of f0F2 for the same UT on all the magnetically quiet days (Ap< 6) within 15 days around the IMF Bz turnings. This yields the deviation from the average quiet-time value ?f0F2. The data are sorted according to the polarity of the IMF Bz and the effects of the southward turnings are discussed. Hapgood et al. (1991), Tulunay et al. (1991), Tulunay and Rahman (1992) investigated the possible effects of the IMF on mid-latitude ionosphere by employing the Slough and Argentine Islands f0F2 data. In order to facilitate a comparison the same method of analysis is being adopted again. However, in the present work the southward polarity changes in IMF Bz with no consideration of the IMF sector structure were considered only.

scholarly journals Long Term Evolution of Solar Sector Structure

1976 ◽  
Vol 71 ◽  
pp. 135-135
Author(s):  
Leif Svalgaard ◽  
John M. Wilcox
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Rotation Period ◽  
Sunspot Cycle ◽  
The Sun ◽  
Sector Structure ◽  
Sunspot Maximum ◽  
The Past

The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles, with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given.

Periodic cosmic-ray variations associated with the sector structure of the interplanetary magnetic field

1968 ◽  
Vol 46 (10) ◽  
pp. S966-S969 ◽  
Author(s):  
V. L. Patel ◽  
R. L. Chasson
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Neutron Monitor ◽  
Cosmic Ray ◽  
Sector Structure ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Neutron Monitor Data ◽  
Monitor Data

Observations by IMP-1 satellite have established that the interplanetary magnetic field is divided into sectors of opposing polarity. These observations have been confirmed by observations with IMP-2 and Mariner 4. The effect of this sector structure on the cosmic-ray intensity observed on the earth has been studied using daily averages of pressure-corrected neutron monitor data from several locations. These data have been analyzed using the method of superposition of epochs, beginning at the edge of the observed sector. The results indicate periodic variations of 6–8-day periods and 0.5 to 1.0% amplitude in cosmic-ray intensity, associated with the passage of positive and negative sectors moving past the earth, including a weak recurrence at 27 days. Theoretical implications of these observations are discussed.

scholarly journals Interplanetary magnetic field and its possible effects on the mid-latitude ionosphere III

1996 ◽  
Vol 39 (4) ◽  
Author(s):  
Y. Tulunay
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Interplanetary Magnetic Field ◽  
Seasonal Effects ◽  
Ionospheric Variability ◽  
Winter Anomaly ◽  
The Mean ◽  
The Imf

Using critical frequencies, f0F2 from the Lannion, Slough, Poitiers, Garchy, Dourbes, Rome, Juliusrud, Gibilmanna, Pruhonice, Uppsala, Kaliningrad, Miedzeszyn, Sofia, Athens and Kiev ionosonde stations, the possible effects of the orientation of the Interplanetary Magnetic Field (IMF) on mid-latitude ionosphere are further investigated. This time, only the southward polarity changes in IMF Bz with seasonal effects were considered. The same method of analysis was employed to facilitate a comparison between the recent results presented here with those which appeared in the preceding papers in the series. That is, the regular diurnal, seasonal and solar cycle variations in the f0F2 data were removed by subtracting the mean of the f0F2 for the same UT on all magnetically quite days (Ap < 6) within 15 days around the IMF Bz turnings (Tulunay, 1994). This last paper also includes the seasonal effects on the ionospheric data. The results confirm that much of the day-to-day variability of the mid-latitude ionosphere may be related to the orientation of the southward IMF Bz , characterized by the ionospheric winter anomaly. Day-to-day ionospheric variability becomes more significant towards higher latitudes.

scholarly journals Cellular automata model of magnetospheric-ionospheric coupling

2003 ◽  
Vol 21 (9) ◽  
pp. 1931-1938 ◽  
Author(s):  
B. V. Kozelov ◽  
T. V. Kozelova
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Cellular Automata ◽  
Interplanetary Magnetic Field ◽  
Control Parameter ◽  
Energy Content ◽  
Nonlinear Phenomena ◽  
Cellular Automata Model ◽  
The Earth ◽  
Magnetospheric Tail

Abstract. We propose a cellular automata model (CAM) to describe the substorm activity of the magnetospheric-ionospheric system. The state of each cell in the model is described by two numbers that correspond to the energy content in a region of the current sheet in the magnetospheric tail and to the conductivity of the ionospheric domain that is magnetically connected with this region. The driving force of the system is supposed to be provided by the solar wind that is convected along the two boundaries of the system. The energy flux inside is ensured by the penetration of the energy from the solar wind into the array of cells (magnetospheric tail) with a finite velocity. The third boundary (near to the Earth) is closed and the fourth boundary is opened, thereby modeling the flux far away from the tail. The energy dissipation in the system is quite similar to other CAM models, when the energy in a particular cell exceeds some pre-defined threshold, and the part of the energy excess is redistributed between the neighbouring cells. The second number attributed to each cell mimics ionospheric conductivity that can allow for a part of the energy to be shed on field-aligned currents. The feedback between "ionosphere" and "magnetospheric tail" is provided by the change in a part of the energy, which is redistributed in the tail when the threshold is surpassed. The control parameter of the model is the z-component of the interplanetary magnetic field (Bz IMF), "frozen" into the solar wind. To study the internal dynamics of the system at the beginning, this control parameter is taken to be constant. The dynamics of the system undergoes several bifurcations, when the constant varies from - 0.6 to - 6.0. The Bz IMF input results in the periodic transients (activation regions) and the inter-transient period decreases with the decrease of Bz. At the same time the onset of activations in the array shifts towards the "Earth". When the modulus of the Bz IMF exceeds some threshold value, the transition takes place from periodic to chaotic dynamics. In the second part of the work we have chosen as the source the real values of the z-component of the interplanetary magnetic field taken from satellite observations. We have shown that in this case the statistical properties of the transients reproduce the characteristic features observed by Lui et al. (2000).Key words. Magnetospheric physics (magnetosphere-ionosphere interactions) – Space plasma physics (nonlinear phenomena)

scholarly journals Sector Structure of the Solar Magnetic Field

1971 ◽  
Vol 43 ◽  
pp. 744-753 ◽  
Author(s):  
John M. Wilcox
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Photospheric Magnetic Field ◽  
The Other ◽  
The Sun ◽  
Sector Structure ◽  
Sector Boundary ◽  
The North

The solar sector structure consists of a boundary in the north-south direction such that on one side of the boundary the large-scale weak photospheric magnetic field is predominantly directed out of the Sun, and on the other side of the boundary this field is directed into the Sun. The region westward of a solar sector boundary tends to be unusually quiet and the region eastward of a solar sector boundary tends to be unusually active. This tendency is discussed in terms of flares, coronal enhancements, plage structure and geomagnetic response.

scholarly journals Ionospheric response to the interplanetary magnetic field southward turning: Fast onset and slow reconfiguration

2002 ◽  
Vol 107 (A8) ◽  
pp. SIA 2-1-SIA 2-9 ◽  
Author(s):  
G. Lu ◽  
T. E. Holzer ◽  
D. Lummerzheim ◽  
J. M. Ruohoniemi ◽  
P. Stauning ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Ionospheric Response ◽  
Fast Onset
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