MAGNETIC FIELD AND RADIAL VELOCITY FLOWS

AT THE INITIAL STAGES OF DEVELOPMENT OF ACTIVE REGIONS BASED ON PHOTOSPHERIC OBSERVATIONS

Aidar M Sadykov, Sergei A Krasotkin

LOMONOSOW MOSCOW STATE UNIVERSITY

DEPARTMENT OF PHYSICS

SPACE PHYSICS BRANCH

IAU Symposium 365 “Dynamics of Solar and Stellar Convection Zones and Atmospheres”

Yerevan, Armenia, 21-25 August 2023

Primary goal: comparison of observations of the magnetic field and radial velocity at the initial stages of Active Region (AR) development and validation of the magnetic flux emergence hypothesis (emerging magnetic flux tube hypothesis)

​

Relevance of this work is determined by the importance of reviewing the current understanding of the magnetic flux emergence, especially at the early stages of the AR formation. There are many theoretical works that inherently assume the idea of magnetic flux tube emergence in ARs. In this situation, the need to verify the correctness of the concepts of the magnetic flux emergence during AR formation (which are taken for granted in many theoretical studies) based on spatially-resolved magnetometric and Doppler observations of the Sun becomes evident

Specific Tasks:

1) Formulation of requirements for available magnetic field and Doppler velocity measurements, data selection, sampling, and preprocessing;

2) Calculation of magnetic field and radial velocity fluxes for the selected sample of ARs;

3) Calculation of the average characteristics of a ‘typical’ AR within our selection. The average characteristics are the temporal evolution of the average values of magnetic field fluxes and radial velocities;

4) Comparison of fluxes of the magnetic fields and radial velocities;

5) Verification of the hypothesis of magnetic flux tube emergence based on the obtained comparison results.

List of active regions

(a)

Example of the (a) evolution of the AR NOAA 11158, and (b) the recognition of quiet Sun/AR areas.

The recognized AR area is indicated in white in panel (b).

(b)

Synchronization scheme of the data with respect to the moment of a sharp increase in magnetic flux.

The moments t1, t2, and t3 corresponding to a sharp increase are all synchronized and shifted to the time moment t0 in the reference timeframe.

t₁

t₂

t₃

t₀

t

t

t

J_mag

J_mag

J_mag

Unsigned magnetic flux in a unified time reference system. The moment t=0 hours corresponds to the moment of sharp increase of the magnetic flux.

(a) Upflow radial velocity flux and (b) downflow radial velocity flux as functions of time.

(a)

(b)

where:

J₊ - upflow radial velocity flux,

J_- - downflow radial velocity flux.

Imbalance of radial velocity fluxes as a function of time

Imbalance of radial velocity fluxes

Imbalance of radial velocity fluxes as a function of the magnetic flux

(a) Upflow radial velocity flux and (b) downflow radial velocity flux as functions of the unsigned magnetic flux.

(a)

(b)

• There was no increase in the upward radial velocity flux found at the initial stages of AR development. Contrary, the growth of the magnetic field flux is accompanied by an increase in the downward radial velocity flux.
• The hypothesis of the magnetic flux tube emergence implies an increase in the magnetic field flux synchronously with an increase in the upward radial velocity flux. No synchronous changes in the upward radial velocity and magnetic field fluxes consistent with the emerging magnetic flux model were identified from the analysis of the ARs under consideration.
• The emerging magnetic flux model cannot be used to describe the evolution of AR, at least in the early stages of its development. This suggests that the processes occurring during the AR formation phase are of a local, rather than global, nature.

Conclusions:

Thank you for your attention!

Суммарный поток радиальной скорости вещества в зависимости от времени

Суммарный поток радиальной скорости вещества в зависимости от потока магнитного поля

Площадь АО в зависимости от потока магнитного поля

NOAA 12494

NOAA 12778

NOAA 12757

NOAA 12827

NOAA 12804

NOAA 12733

NOAA 12715

NOAA 12581