The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform

Hannes Vomhoff - One of the best experts on this subject based on the ideXlab platform.

M V Nikonova - One of the best experts on this subject based on the ideXlab platform.

  • line of sight Velocity measurements using a dissector tube ii time variations of the Tangential Velocity Component in the evershed effect
    Astronomy and Astrophysics, 1993
    Co-Authors: S A Druzhinin, Alexei A Pevtsov, V L Levkovsky, M V Nikonova
    Abstract:

    We present the results of measurements of sunspot torsional oscillations. For six sunspots, a study was made of the spectral composition of Doppler Velocity signals from two areas of penumbra, symmetric about the sunspot umbra located near the limb. The spectrograph slit was directed parallel to the nearest solar limb. The observations were made in the lines Fe I 543.45 nm and Hβ 486.13 nm using a dissector tube. Its electronic scanning was controlled in such a way that two channels measure spectral line shifts in two different parts of the photocathode. Attention mainly was paid to periods from 1 min to several hours

Jonas Ergstrom - One of the best experts on this subject based on the ideXlab platform.

S A Druzhinin - One of the best experts on this subject based on the ideXlab platform.

  • line of sight Velocity measurements using a dissector tube ii time variations of the Tangential Velocity Component in the evershed effect
    Astronomy and Astrophysics, 1993
    Co-Authors: S A Druzhinin, Alexei A Pevtsov, V L Levkovsky, M V Nikonova
    Abstract:

    We present the results of measurements of sunspot torsional oscillations. For six sunspots, a study was made of the spectral composition of Doppler Velocity signals from two areas of penumbra, symmetric about the sunspot umbra located near the limb. The spectrograph slit was directed parallel to the nearest solar limb. The observations were made in the lines Fe I 543.45 nm and Hβ 486.13 nm using a dissector tube. Its electronic scanning was controlled in such a way that two channels measure spectral line shifts in two different parts of the photocathode. Attention mainly was paid to periods from 1 min to several hours

Elena Provornikova - One of the best experts on this subject based on the ideXlab platform.

  • plasma flows in the heliosheath along the voyager 1 and 2 trajectories due to effects of the 11 yr solar cycle
    The Astrophysical Journal, 2014
    Co-Authors: Elena Provornikova, M Opher, V V Izmodenov, J D Richardson, G Toth
    Abstract:

    We investigate the role of the 11 yr solar cycle variations in the solar wind (SW) parameters on the flows in the heliosheath using a new three-dimensional time-dependent model of the interaction between the SW and the interstellar medium. For boundary conditions in the model we use realistic time and the latitudinal dependence of the SW parameters obtained from SOHO/SWAN and interplanetary scintillation data for the last two solar cycles (1990-2011). This data set generally agrees with the in situ Ulysses measurements from 1991 to 2009. For the first ∼30 AU of the heliosheath the time-dependent model predicts constant radial flow speeds at Voyager 2 (V2), which is consistent with observations and different from the steady models that show a radial speed decrease of 30%. The model shows that V2 was immersed in SW with speeds of 500-550 km s{sup –1} upstream of the termination shock before 2009 and in wind with upstream speeds of 450-500 km s{sup –1} after 2009. The model also predicts that the radial Velocity along the Voyager 1 (V1) trajectory is constant across the heliosheath, contrary to observations. This difference in observations implies that additional effects may be responsible for the different flows at V1more » and V2. The model predicts meridional flows (VN) higher than those observed because of the strong bluntness of the heliosphere shape in the N direction in the model. The modeled Tangential Velocity Component (VT) at V2 is smaller than observed. Both VN and VT essentially depend on the shape of the heliopause.« less