A5050765864- Solar and Space Plasma Dynamics
- Radio Astronomy Observations and Technology
- Ionosphere and magnetosphere dynamics
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Spacecraft Design and Technology
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- GNSS positioning and interference
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Earthquake Detection and Analysis
- Astronomy and Astrophysical Research
- Antenna Design and Optimization
- Geomagnetism and Paleomagnetism Studies
- Solar Radiation and Photovoltaics
- Galaxies: Formation, Evolution, Phenomena
- Superconducting and THz Device Technology
- Radio Wave Propagation Studies
- Atmospheric Ozone and Climate
- Inertial Sensor and Navigation
- Hydraulic and Pneumatic Systems
- Space exploration and regulation
- Dynamics and Control of Mechanical Systems
- Space Satellite Systems and Control
Savitribai Phule Pune University
2012-2023
Tata Institute of Fundamental Research
1987-2013
Institute of Radio Astronomy
2009
National Centre for Radio Astrophysics
1995-2007
Pathways Behavioral Services
2001-2005
Eaton (United States)
1996-2002
Nagoya University
1999-2002
Dynamic Systems (United States)
1990
National Radio Astronomy Observatory
1990
Iowa State University
1989
We present a comparison of spacecraft and IPS measurements the solar wind velocity for 1973–75, when large scale structure was very stable. From this we infer prototype distribution across high‐speed stream electron density fluctuations Δn e in spatial frequency range 10 −4 –10 −2 km −1 . This ‘microturbulence’ is more closely related to than bulk n p Enhancements occur interaction region, but they are not as those peak 12 hours after peak. The similar that (10 6 km) magnetic field σ B ,...
We report observations of a steady 20 year decline solar photospheric fields at latitudes $\geq$45${^{o}}$ starting from $\sim$1995. This prolonged and continuing decline, combined with the fact that Cycle 24 is already past its peak, implies magnetic are likely to continue until $\sim$2020, expected minimum ongoing 24. In addition, interplanetary scintillation (IPS) inner heliosphere for period 1983--2013 in distance range 0.2--0.8 AU, have also shown similar wind micro-turbulence levels,...
A prediction-based feedforward filter has been developed to make a ground-based hydraulic simulator generate contact forces and rebound velocities that match those expected during Shuttle on-orbit berthing operations.
Abstract Extensive interplanetary scintillation (IPS) observations at 327 MHz obtained between 1983 and2009 clearly show a steady and significant drop in the turbule nce levels entire inner heliospherestarting from around ∼1995. We believe that this large-scale IPS signature, theinner heliosphere,coupledwith thefact thatsolarpolarfields have alsobeen de cliningsince∼1995, providea consistentresult showing buildup to deepest minimum 100 years actually began more than adecade earlier....
The ratio of the rms electron density fluctuations to background in solar wind (density modulation index, $\epsilon_{N} \equiv \Delta{N}/N$) is vital importance understanding several problems heliospheric physics related turbulence. In this paper, we have investigated behavior $\epsilon_{N}$ inner-heliosphere from 0.26 0.82 AU. $\Delta{N}$ been deduced using extensive ground-based observations interplanetary scintillation (IPS) at 327 MHz, which probe spatial scales a few hundred km....
We report first results from an ongoing program of combining visibilities the Giant Meterwave Radio Telescope () and Nancay Heliograph to produce composite snapshot images sun at meter wavelengths. describe data processing, including a specific multi-scale algorithm. present a) simulations for two models 327 MHz, with differing complexity b) observations complex noise storm on MHz Aug. 27, 2002. Our illustrate capacity this method high dynamic range when solar corona has structures scales...
Abstract We examine the temporal changes in both solar polar magnetic field (PMF) at latitudes ≥45° and heliospheric (HMF) 1 AU during cycles 21–24 with emphasis on recent activity after July 2015, so called “mini maximum” of cycle 24. While unsigned PMF shows modulations 21 22, it an anti‐correlation variation In addition, floor level HMF (of 4.6 nT), that is, value returns to each minimum, is breached about 2 years prior 24 indicating a reduced 3.2 ± 0.5 nT upcoming minimum. light change...
The properties of the interplanetary medium and structures of9 compact radio sources have been derived from observed scintillations at 327 MHz using Ooty telescope. scale size electron density irregularities has a value 100 km in elongation range 0�3-0� 7 A. U. shows no indication increasing with elongation, as suggested by Hewish Symonds (1969). Bessel transforms intensity fluctuations could seldom be used for estimating solar wind velocity since minima corresponding to Fresnel filtering...
We discuss a filament eruption/coronal mass ejection (CME) event associated with flare of GOES class M2.8 that occurred on 2001 November 17. This was observed by the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz. NoRH during its eruption both as dark feature against solar disk bright above limb. The high cadence radio data allows us to follow motion time resolution height more than half radius. shows very gradual onset then rapid acceleration phase coincident launch fast halo CME. Soft...
We report new radio continuum and 21 cm HI observations using the Giant Metrewave Radio Telescope (GMRT) of group Holmberg 124 (Ho 124) comprising four late-type galaxies, namely NGC 2820, Mrk 108, 2814 2805. The three 108 which are closely located in sky plane have clearly undergone tidal interactions as seen from various morphological signatures debris. Moreover we note features members believe might be due to ram pressure. In this paper, describe interesting results emerging our...
Ionospheric total electron content (TEC) and scintillations have been recorded continuously since April 2003 using a dual‐frequency GPS receiver at Pune, India (geographic latitude 19.1°N, longitude 74.05°E; 24°N dip), situated in between the magnetic equator northern crest of equatorial anomaly. The TEC often shows bite‐outs when severe amplitude are observed on L1 carrier level. apparent duration may be different from true east‐west duration, as with geostationary links, because presence...
We report extensive interplanetary scintillation (IPS) observations of the solar wind during period centered around 11 May 1999, when Earth was engulfed by a region with unusually low densities (<1 cm −3 ) and velocities (<350 km s −1 ). IPS Ooty Radio Telescope (ORT), operating at 327 MHz, probe inner heliosphere along large number closely spaced lines sight over heliocentric distance range 0.2 to 1.0 AU, daily, rate about 150 sources in course 10 hours. Using these observations,...