scholarly journals Influence of solar activity on magnetic network measurements

2013 ◽  
Vol 55 (6) ◽  
Author(s):  
Roberta Tozzi ◽  
Guido Dominici ◽  
Paola De Michelis ◽  
Antonio Meloni
Keyword(s):  
Solar Activity ◽  
Ring Current ◽  
Solar Maximum ◽  
Magnetic Measurements ◽  
High Solar Activity ◽  
Repeat Station ◽  
External Contribution ◽  
The Difference ◽  
The Magnetic Field ◽  
Magnetic Network

<p>The influence of solar activity on magnetic measurements taken during the Italian repeat station surveys performed in 1999/2000 and 2009/2010 has been investigated. A method to estimate the difference between the 2000.0 and 2010.0 surveys in terms of the "residual" (i.e. not completely reduced) external contribution is proposed. This method is also based on the removal of the contribution due to the magnetic field of internal origin by means of CHAOS3 model from magnetic repeat station measurements. The origin of the observed differences is interpreted in terms of the very different level of solar activity between 2000.0 and 2010.0. Indeed, results seem to suggest that differences could be attributed to the enhanced ring current intensity during a phase of solar maximum. The investigation of the spatial patterns of these differences suggests that they could be reduced by introducing a larger number of variometer stations, especially during surveys performed under conditions of high solar activity.</p>

scholarly journals THE STRUCTURE OF THE SOLAR WIND IN THE HELIOSPHERE DEPENDING ON THE PHASE OF THE SOLAR CYCLE: LARGE-SCALE DYNAMICS OF THE HELIOSPHERIC CURRENT SHEET

2019 ◽  
Vol 47 (1) ◽  
pp. 85-87
Author(s):  
E.V. Maiewski ◽  
R.A. Kislov ◽  
H.V. Malova ◽  
O.V. Khabarova ◽  
V.Yu. Popov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Activity ◽  
Solar Cycle ◽  
Current Sheet ◽  
Heliospheric Current Sheet ◽  
High Solar Activity ◽  
The Sun ◽  
High Latitudes ◽  
The Magnetic Field

A stationary axisymmetric MHD model of the solar wind has been constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun at almost all heliolatitudes. The model takes into account the changes in the magnetic field of the Sun during a quarter of the solar cycle, when the dominant dipole magnetic field is replaced by a quadrupole. Selfconsistent solutions for the magnetic and velocity fields, plasma concentration and current density of the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the domination of the dipole magnetic component in the solar wind heliospheric current sheet (HCS) is located in the equatorial plane, which is a part of the system of radial and transverse currents, symmetrical in the northern and southern hemispheres. As the relative contribution of the quadrupole component to the total magnetic field increases, the shape of the HCS becomes conical; the angle of the cone gradually decreases, so that the current sheet moves entirely to one of the hemispheres. At the same time, at high latitudes of the opposite hemisphere, a second conical HCS arises, the angle of which increases. When the quadrupole field becomes dominant (at maximum solar activity), both HCS lie on conical surfaces inclined at an angle of 35 degrees to the equator. The model describes the transition from the fast solar wind at high latitudes to the slow solar wind at low latitudes: a relatively gentle transition in the period of low solar activity gives way to more drastic when high solar activity. The model also predicts an increase in the steepness of the profiles of the main characteristics of the solar wind with an increase in the radial distance from the Sun. Comparison of the obtained dependences with the available observational data is discussed.

scholarly journals Modelling of the ring current in Saturn's magnetosphere

2004 ◽  
Vol 22 (2) ◽  
pp. 653-659 ◽  
Author(s):  
G. Giampieri ◽  
M. K. Dougherty
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Current Model ◽  
Temporal Variations ◽  
Data Sets ◽  
Data Set ◽  
Equatorial Current ◽  
The Difference ◽  
Current Systems ◽  
The Magnetic Field

Abstract. The existence of a ring current inside Saturn's magnetosphere was first suggested by Smith et al. (1980) and Ness et al. (1981, 1982), in order to explain various features in the magnetic field observations from the Pioneer 11 and Voyager 1 and 2 spacecraft. Connerney et al. (1983) formalized the equatorial current model, based on previous modelling work of Jupiter's current sheet and estimated its parameters from the two Voyager data sets. Here, we investigate the model further, by reconsidering the data from the two Voyager spacecraft, as well as including the Pioneer 11 flyby data set. First, we obtain, in closed form, an analytic expression for the magnetic field produced by the ring current. We then fit the model to the external field, that is the difference between the observed field and the internal magnetic field, considering all the available data. In general, through our global fit we obtain more accurate parameters, compared to previous models. We point out differences between the model's parameters for the three flybys, and also investigate possible deviations from the axial and planar symmetries assumed in the model. We conclude that an accurate modelling of the Saturnian disk current will require taking into account both of the temporal variations related to the condition of the magnetosphere, as well as non-axisymmetric contributions due to local time effects. Key words. Magnetospheric physics (current systems; planetary magnetospheres; plasma sheet)

scholarly journals Dusk-to-nighttime enhancement of mid-latitude <i>Nm</i>F2 in local summer: inter-hemispheric asymmetry and solar activity dependence

2015 ◽  
Vol 33 (6) ◽  
pp. 711-718 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
H. Le ◽  
W. Wan ◽  
H. Zhang
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Peak Height ◽  
Activity Level ◽  
High Solar Activity ◽  
Activity Levels ◽  
Solar Activity Level ◽  
Latitudinal Dependence ◽  
The Difference

Abstract. In this paper ionosonde observations in the East Asia–Australia sector were collected to investigate dusk-to-nighttime enhancement of mid-latitude summer NmF2 (maximum electron density of the F2 layer) within the framework of NmF2 diurnal variation. NmF2 were normalized to two solar activity levels to investigate the dependence of the dusk-to-nighttime enhancement on solar activity. The dusk-to-nighttime enhancement of NmF2 is more evident at Northern Hemisphere stations than at Southern Hemisphere stations, with a remarkable latitudinal dependence. The dusk-to-nighttime enhancement shows both increasing and declining trends with solar activity increasing, which is somewhat different from previous conclusions. The difference in the dusk-to-nighttime enhancement between Southern Hemisphere and Northern Hemisphere stations is possibly related to the offset of the geomagnetic axis from the geographic axis. hmF2 (peak height of the F2 layer) diurnal variations show that daytime hmF2 begins to increase much earlier at low solar activity level than at high solar activity level at northern Akita and Wakkanai stations where the dusk-to-nighttime enhancement is more prominent at low solar activity level than at high solar activity level. That implies neutral wind phase is possibly also important for nighttime enhancement.

HIGH-ALTITUDE COSMIC RAY MEASUREMENTS AT FORT CHURCHILL

1960 ◽  
Vol 38 (5) ◽  
pp. 638-641 ◽  
Author(s):  
I. B. McDiarmid ◽  
D. C. Rose
Keyword(s):  
Solar Activity ◽  
High Altitude ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cosmic Ray ◽  
Geiger Counter ◽  
Low Energy ◽  
High Solar Activity ◽  
Energy Radiation ◽  
Cosmic Ray Intensity

Measurements with rocket-borne Geiger counters have been carried out at altitudes up to 250 km at Fort Churchill, Manitoba. The total primary cosmic ray intensity at a time near a solar maximum has been determined and compared with other measurements taken at times of high solar activity and also with other Geiger counter measurements obtained near a solar minimum. A low-energy radiation was observed whose intensity increased with altitude up to about 25% of the primary intensity at 250 km.

Irradiance Observations of the Sun

1994 ◽  
Vol 143 ◽  
pp. 28-36 ◽  
Author(s):  
Claus Fröhlich
Keyword(s):  
Solar Activity ◽  
Time Scales ◽  
Solar Maximum ◽  
Activity Cycle ◽  
Total Solar Irradiance ◽  
The Sun ◽  
Direct Influence ◽  
Magnetic Network ◽  
Over Time

Measurements of the total solar irradiance during the last 14 years from satellites show variations over time scales from minutes to years and decades. The most important variance is in the range from days to several months and is related to the photospheric features of solar activity: decreasing the irradiance during the appearance of sunspots, and increasing it by faculae and the bright magnetic network. Long-term modulation by the 11-year activity cycle is observed conclusively with the irradiance being higher during solar maximum. The accuracy of the determined variability and its interpretation in terms of manifestations of activity related features on the photosphere is discussed. Besides the direct influence of the spots, faculae and magnetic network more profound changes in the thermal transport seem to influence the behaviour of the solar photospheric radiation on the solar cycle and longer time scales.

scholarly journals Lonosphere-thermosphere Relation as Seen in Measured and Modeled Electron and Neutral Densities

2021 ◽  
Author(s):  
Kristin Vielberg ◽  
Armin Corbin ◽  
Jürgen Kusche ◽  
Chao Xiong ◽  
Claudia Stolle
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Geomagnetic Latitude ◽  
High Solar Activity ◽  
Data Sets ◽  
Electron Densities ◽  
Good Opportunity ◽  
Density Anomaly ◽  
The Difference ◽  
Correlation Properties

Abstract The availability of in-situ neutral and electron densities along the orbit of the satellite missions GRACE and CHAMP provide a good opportunity to study the ionosphere-thermosphere (IT) system. The aim of this paper is (1) to use these data sets, to study the IT density relation empirically via correlation properties for different conditions depending on solar activity, geomagnetic latitude, and local time and (2) to verify whether these relations are consistent with the output of the TIE-GCM model of the thermosphere and ionosphere. Our results show that the correlations of electron and neutral densities strongly depend on magnetic local time (MLT) with a minimal correlation between 6-9h MLT, e.g., every 131 days for CHAMP around 400km altitude and every 160 days for GRACE around 500km. During low solar activity, the correlation of modeled and measured densities agrees well for both satellites. On the contrary, we note that the correlations between the modeled values are higher, especially during high solar activity, where the difference between correlations of modeled and measured densities is about 0.2. We suggest that the reason for this misalignment might be related to the poor representation of the equatorial density anomaly in the model especially during high solar activity. We believe our results will be useful for studies that aim at assimilating electron densities into a physical model to improve the prediction of neutral densities, since the skill of data assimilation depends to a large extent on the representation of the correlation between both densities.

scholarly journals Equinoctial asymmetry in solar activity variations of <I>Nm</I>F2 and TEC

2012 ◽  
Vol 30 (3) ◽  
pp. 613-622 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
W. Wan ◽  
Z. Ren
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
High Solar Activity ◽  
Solar Cycles ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Increase Rate ◽  
Dip Equator ◽  
The Difference

Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.

VARIATIONS IN TOTAL ELECTRON CONTENT DURING THE PHASES OF LOW AND HIGH SOLAR ACTIVITIES

2016 ◽  
Vol 78 (5-8) ◽  
Author(s):  
Mariyam Jamilah Homam ◽  
Mohamad Aizat Ezri Ahmad Hapizudin
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Solar Minimum ◽  
Solar Maximum ◽  
High Solar Activity ◽  
Electron Content ◽  
Minimum Phase ◽  
Maximum Phase ◽  
Total Electron ◽  
Value Changes

Variations in the Total Electron Content of the ionosphere were studied by utilizing data from the GISTM receiver installed at Universiti Tun Hussein Onn Malaysia. The study was conducted during periods of low solar activity (July 2007–July 2008) and high solar activity (July 2013–July 2014). Results show that the TEC are dependent on the solar activity.The values during high solar activity were significantly higher than that obtained during the solar minimum phase. The minimum TEC values for both phases varied between 89% and 97%, and the maximum TEC values varied between 70% and 81%. The pattern of daily TEC value changes was constant, and TEC peaked in the afternoon at ~14 LT. The highest TEC recorded during the solar maximum phase was 144.5 TEC Unit (TECU) in April 2014, whereas the highest TEC recorded during the solar minimum phase was 36.3 TECU in April 2008. TEC was maximized from March to May under both solar maximum and minimum phases.

scholarly journals First in-orbit results of the vector magnetic field measurement of the High Precision Magnetometer onboard the China Seismo-Electromagnetic Satellite

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Bin Zhou ◽  
Bingjun Cheng ◽  
Xiaochen Gou ◽  
Lei Li ◽  
Yiteng Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Precision ◽  
Magnetic Field Measurement ◽  
Vector Data ◽  
Magnetic Field Data ◽  
Night Side ◽  
The Difference ◽  
The Magnetic Field ◽  
Ground Calibration ◽  
Data Calibration

Abstract The High Precision Magnetometer (HPM) is one of the main payloads onboard the China Seismo-Electromagnetic Satellite (CSES). The HPM consists of two Fluxgate Magnetometers (FGM) and the Coupled Dark State Magnetometer (CDSM), and measures the magnetic field from DC to 15 Hz. The FGMs measure the vector components of the magnetic field; while the CDSM detects the magnitude of the magnetic field with higher accuracy, which can be used to calibrate the linear parameters of the FGM. In this paper, brief descriptions of measurement principles and performances of the HPM, ground, and in-orbit calibration results of the FGMs are presented, including the thermal drift and magnetic interferences from the satellite. The HPM in-orbit vector data calibration includes two steps: sensor non-linearity corrections based on on-ground calibration and fluxgate linear parameter calibration based on the CDSM measurements. The calibration results show a reasonably good stability of the linear parameters over time. The difference between the field magnitude calculated from the calibrated FGM components and the magnitude directly measured by the CDSM is just 0.5 nT (1σ) when the linear parameters are fitted separately for the day- and the night-side. Satellite disturbances have been analyzed including soft and hard remanence as well as magnetization of the magnetic torquer, radiation from the Tri-Band Beacon, and interferences from the rotation of the solar wing. A comparison shows consistency between the HPM and SWARM magnetic field data. Observation examples are introduced in the paper, which show that HPM data can be used to survey the global geomagnetic field and monitor the magnetic field disturbances in the ionosphere.

Sign in / Sign up

Export Citation Format

Share Document