scholarly journals Observations of interplanetary scintillation during the 1998 Whole Sun Month: a comparison between EISCAT, ORT and Nagoya data

2000 ◽  
Vol 18 (9) ◽  
pp. 1003-1008 ◽  
Author(s):  
P. J. Moran ◽  
S. Ananthakrishnan ◽  
V. Balasubramanian ◽  
A. R. Breen ◽  
A. Canals ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Velocity ◽  
Solar Physics ◽  
Solar Wind Plasma ◽  
Interplanetary Scintillation ◽  
Velocity Measurements ◽  
Plasma Sources ◽  
Interplanetary Physics ◽  
Instruments And Techniques ◽  
Good Agreement

Abstract. Observations of interplanetary scintillation (IPS) allow accurate solar wind velocity measurements to be made at all heliographic latitudes and at a range of distances from the Sun. The data may be obtained with either single, double or multiple antennas, each requiring a different method of analysis. IPS data taken during the 1998 whole sun month (30th July-31st August 1998) by EISCAT, the ORT (Ooty Radio Telescope), India, and the Nagoya IPS system, Japan, allow the results of individual methods of analysis to be compared. Good agreement is found between the velocity measurements using each method, and when combined an improved understanding of the structure of the solar wind can be obtained.Key words: Interplanetary physics (solar wind plasma; sources of the solar wind) - Solar physics, astrophysics and astronomy (instruments and techniques)

scholarly journals EISCAT measurements of solar wind velocity and the associated level of interplanetary scintillation

2002 ◽  
Vol 20 (9) ◽  
pp. 1279-1289 ◽  
Author(s):  
R. A. Fallows ◽  
P. J. S. Williams ◽  
A. R. Breen
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Solar Wind Plasma ◽  
Scintillation Index ◽  
Line Of Sight ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Interplanetary Physics ◽  
Eiscat Measurements

Abstract. A relative scintillation index can be derived from EISCAT observations of Interplanetary Scintillation (IPS) usually used to study the solar wind velocity. This provides an ideal opportunity to compare reliable measurements of the solar wind velocity derived for a number of points along the line-of-sight with measurements of the overall level of scintillation. By selecting those occasions where either slow- or fast-stream scattering was dominant, it is shown that at distances from the Sun greater than 30 RS , in both cases the scintillation index fell with increasing distance as a simple power law, typically as R-1.7. The level of scintillation for slow-stream scattering is found to be 2.3 times the level for fast-stream scattering.Key words. Interplanetary physics (solar wind plasma)

Solar Orbiter observations of solar wind current sheets and their deHoffman-Teller frames

2021 ◽  
Author(s):  
Konrad Steinvall ◽  
Yuri Khotyaintsev ◽  
Giulia Cozzani ◽  
Andris Vaivads ◽  
Christopher Owen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Field Measurements ◽  
Velocity Measurements ◽  
Current Sheets ◽  
Spacecraft Orbit ◽  
Electric Field Measurements ◽  
Good Agreement

<p>Solar wind current sheets have been extensively studied at 1 AU. The recent advent of Parker Solar Probe and Solar Orbiter (SolO) has enabled us to study these structures at a range of heliocentric distances.</p><p>We present SolO observations of current sheets in the solar wind at heliocentric distances between 0.55 and 0.85 AU, some of which show signatures of ongoing magnetic reconnection. We develop a method to find the deHoffman-Teller frame which minimizes the Y-component (the component tangential to the spacecraft orbit) of the electric field. Using the electric field measurements from RPW and magnetic field measurements from MAG, we use our method to determine the deHoffman-Teller frame of solar wind current sheets. The same method can also be used on the Alfvénic turbulence and structures found in the solar wind to obtain a measure of the solar wind velocity.</p><p>Our preliminary results show a good agreement between our modified deHoffmann-Teller analysis based on the single component E-field, and the conventional deHoffman-Teller analysis based on 3D plasma velocity measurements from PAS. This opens up the possibility to use the RPW and MAG data to obtain an estimate of the solar wind velocity when particle data is unavailable.</p>

scholarly journals Simultaneous interplanetary scintillation and optical measurements of the acceleration of the slow solar wind

2000 ◽  
Vol 18 (9) ◽  
pp. 995-1002 ◽  
Author(s):  
A. R. Breen ◽  
S. J. Tappin ◽  
C. A. Jordan ◽  
P. Thomasson ◽  
P. J. Moran ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Plasma ◽  
Optical Measurements ◽  
Slow Solar Wind ◽  
Wind Instruments ◽  
Interplanetary Physics ◽  
Instruments And Techniques ◽  
Average Profile ◽  
Soho Spacecraft ◽  
Made In

Abstract. Simultaneous observations of the slow solar wind off the southeast limb of the Sun were made in May 1999 using optical measurements from the C2 and C3 LASCO coronagraphs on board the SOHO spacecraft and radio-scattering measurements from the MERLIN and EISCAT facilities. The observations show the slow solar wind accelerating outwards from 4.5 solar radii (R), reaching a final velocity of 200-300 km s-1 by 25-30 R. The acceleration profile indicated by these results is more gentle than the average profile seen in earlier LASCO observations of larger scale features, but is within the variation seen in these studies.Key words: Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques)

scholarly journals Estimating random transverse velocities in the fast solar wind from EISCAT Interplanetary Scintillation measurements

2002 ◽  
Vol 20 (9) ◽  
pp. 1265-1277 ◽  
Author(s):  
A. Canals ◽  
A. R. Breen ◽  
L. Ofman ◽  
P. J Moran ◽  
R. A Fallows
Keyword(s):  
Solar Wind ◽  
Transverse Velocity ◽  
A Priori ◽  
Solar Wind Plasma ◽  
Flow Speed ◽  
Mhd Waves ◽  
Interplanetary Scintillation ◽  
Fast Solar Wind ◽  
Interplanetary Physics ◽  
Made In

Abstract. Interplanetary scintillation measurements can yield estimates of a large number of solar wind parameters, including bulk flow speed, variation in bulk velocity along the observing path through the solar wind and random variation in transverse velocity. This last parameter is of particular interest, as it can indicate the flux of low-frequency Alfvén waves, and the dissipation of these waves has been proposed as an acceleration mechanism for the fast solar wind. Analysis of IPS data is, however, a significantly unresolved problem and a variety of a priori assumptions must be made in interpreting the data. Furthermore, the results may be affected by the physical structure of the radio source and by variations in the solar wind along the scintillation ray path. We have used observations of simple point-like radio sources made with EISCAT between 1994 and 1998 to obtain estimates of random transverse velocity in the fast solar wind. The results obtained with various a priori assumptions made in the analysis are compared, and we hope thereby to be able to provide some indication of the reliability of our estimates of random transverse velocity and the variation of this parameter with distance from the Sun.Key words. Interplanetary physics (MHD waves and turbulence; solar wind plasma; instruments and techniques)

scholarly journals Latitudinal extent of large-scale structures in the solar wind

2003 ◽  
Vol 21 (6) ◽  
pp. 1331-1339 ◽  
Author(s):  
H. A. Elliott ◽  
D. J. McComas ◽  
P. Riley
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Spatial Scales ◽  
Coronal Holes ◽  
Solar Wind Plasma ◽  
Ecliptic Plane ◽  
Plasma Parameters ◽  
Field Polarity ◽  
Interplanetary Physics ◽  
Hydrodynamic Code

Abstract. Comparison of solar wind observations from the ACE spacecraft, in the ecliptic plane at ~ 1 AU, and the Ulysses spacecraft as it orbits over the Sun’s poles, provides valuable information about the latitudinal extent and variation of solar wind structures in the heliosphere. While qualitative comparisons can be made using average properties observed at these two locations, the comparison of specific, individual structures requires a procedure to determine if a given structure has been observed by both spacecraft. We use a 1-D hydrodynamic code to propagate ACE plasma measurements out to the distance of Ulysses and adjust for the differing longitudes of the ACE and Ulysses spacecraft. In addition to comparing the plasma parameters and their characteristic profiles, we examine suprathermal electron measurements and magnetic field polarity to help determine if the same features are encountered at both ACE and Ulysses. The He I l 1083 nm coronal hole maps are examined to understand the global structure of the Sun during the time of our heliospheric measurements. We find that the same features are frequently observed when both spacecraft are near the ecliptic plane. Stream structures derived from smaller coronal holes during the rising phase of solar cycle 23 persists over 20°–30° in heliolatitude, consistent with their spatial scales back at the Sun.Key words. Interplanetary physics (solar wind plasma)

scholarly journals Interplanetary Scintillation - Preliminary Observations at 103 MHz

1980 ◽  
Vol 91 ◽  
pp. 405-408
Author(s):  
S. K. Alurkar ◽  
R. V. Bhonsle
Keyword(s):  
Solar Wind ◽  
Solar Wind Plasma ◽  
Scintillation Index ◽  
Interplanetary Scintillation ◽  
Antenna Aperture ◽  
Scale Size ◽  
Intensity Fluctuations

A 3-station interplanetary scintillation (IPS) observatory is being developed mainly with a view to study the solar wind plasma. The first IPS telescope operating at 103 MHz at Thaltej near Ahmedabad has been put into regular operation since April 1979. With only half the antenna aperture (≃2500 m2) presently in use, observations of 8-10 sources are being made to calculate scintillation index, temporal spectrum of intensity fluctuations and scale size of density irregularities.

scholarly journals Dynamical evolution of the inner heliosphere approaching solar activity maximum: interpreting Ulysses observations using a global MHD model

2003 ◽  
Vol 21 (6) ◽  
pp. 1347-1357 ◽  
Author(s):  
P. Riley ◽  
Z. Mikić ◽  
J. A. Linker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Maximum ◽  
Dynamical Evolution ◽  
Solar Wind Plasma ◽  
Polar Regions ◽  
Activity Maximum ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Interaction Regions

Abstract. In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun’s approach toward solar maximum; and (2) Ulysses’ second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses’ first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.Key words. Interplanetary physics (Interplanetary magnetic fields; solar wind plasma; sources of the solar wind)

scholarly journals In situ local shock speed and transit shock speed

1998 ◽  
Vol 16 (4) ◽  
pp. 370-375 ◽  
Author(s):  
S. Watari ◽  
T. Detman
Keyword(s):  
Solar Wind ◽  
Solar Wind Plasma ◽  
Interplanetary Shock ◽  
Propagation Model ◽  
Interplanetary Shocks ◽  
Shock Speed ◽  
Interplanetary Physics ◽  
Speed Solar Wind ◽  
Transit Speed

Abstract. A useful index for estimating the transit speeds was derived by analyzing interplanetary shock observations. This index is the ratio of the in situ local shock speed and the transit speed; it is 0.6–0.9 for most observed shocks. The local shock speed and the transit speed calculated for the results of the magnetohydrodynamic simulation show good agreement with the observations. The relation expressed by the index is well explained by a simplified propagation model assuming a blast wave. For several shocks the ratio is approximately 1.2, implying that these shocks accelerated during propagation in slow-speed solar wind. This ratio is similar to that for the background solar wind acceleration.Keywords. Interplanetary physics (Flare and stream dynamics; Interplanetary shocks; Solar wind plasma)

scholarly journals How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

2003 ◽  
Vol 21 (6) ◽  
pp. 1257-1261 ◽  
Author(s):  
K. Fujiki ◽  
M. Kojima ◽  
M. Tokumaru ◽  
T. Ohmi ◽  
A. Yokobe ◽  
...  
Keyword(s):  
Solar Wind ◽  
Northern Hemisphere ◽  
High Speed ◽  
Solar Maximum ◽  
Complex Structure ◽  
Coronal Holes ◽  
Interplanetary Scintillation ◽  
Wind Structure ◽  
Interplanetary Physics ◽  
Solar Wind Structure

Abstract. Observations from the second Ulysses fast latitude scan show that the global structure of solar wind near solar maximum is much more complex than at solar minimum. Soon after solar maximum, Ulysses observed a polar coronal hole (high speed) plasma with magnetic polarity of the new solar cycle in the Northern Hemisphere. We analyze the solar wind structure at and near solar maximum using interplanetary scintillation (IPS) measurements. To do this, we have developed a new tomographic technique, which improves our ability to examine the complex structure of the solar wind at solar maximum. Our IPS results show that in 1999 and 2000 the total area with speed greater than 700 km s-1 is significantly reduced first in the Northern Hemisphere and then in the Southern Hemisphere. For year 2001, we find that the formation of large areas of fast solar wind around the north pole precedes the formation of large polar coronal holes around the southern pole by several months. The IPS observations show a high level agreement to the Ulysses observation, particularly in coronal holes.Key words. Interplanetary physics (solar wind plasma) – Radio science (remote sensing)

Sign in / Sign up

Export Citation Format

Share Document