Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic fields in M dwarfs: rapid magnetic field variability in EV Lac   We report here our spectropolarimetric observations obtained using the
Espadons/CFHT high resolution spectrograph of two M dwarf stars which standard
models suggest are fully convective: EV Lac (M3.5) and HH And (M5.5). The
difference in their rotational velocity makes them good targets to study the
dependence of the magnetic field topology in M dwarfs on rotation. Our results
reveal some aspects of the field topology in EV Lac and HH And. We measured
mean longitudinal magnetic field strengths (Bz) in EV Lac ranging from 18+-3 G
to -40+-3 G. The Bz variations are seen to occur in a timescale of less than 50
minutes, significantly shorter than the rotation period, and are not due to a
flaring event. We discuss some formation scenarios of the Zeeman signatures
found in EV Lac. For HH And we could not detect circular polarization and thus
we place an upper limit to Bz of 5 G.

29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc