Baryon-Dark matter interaction in presence of magnetic fields in light
  of EDGES signal
  We have shown that in presence of a cosmic magnetic field the bounds on
baryon dark matter cross-section ($\hat \sigma$), dark-matter mass ($m_d$) and
values of the magnetic field ($B_0$) can strongly influence each other. This
requires to rework the bounds on $\hat \sigma\,$, $m_d$ and $B_0$ which can
explain the observed absorption signal by EDGES collaboration. The upper limit
on the magnetic field strength can modify in presence of baryon-dark matter
interaction cross-section. In the presence of a strong magnetic field, a large
baryon-dark matter interaction cross-section is required to balance magnetic
heating of gas to explain the EDGES signal as compared to a weak magnetic
field. Subsequently, the strong magnetic-fields can even erase the 21 cm
signal--this gives an upper bound on the strength of magnetic-fields,
dark-matter mass and baryon-dark matter cross-section. In the special case when
$\hat \sigma$=0, one can recover the bound on magnetic field strength
calculated in [1]. In this work we find that the allowed range of the
primordial magnetic field can increase by three orders of magnitude in
comparison with [1]. We get upper bound on the magnetic field strength:
$3.48\times10^{-6}$ G for the dark matter mass $\lesssim 10^{-2}$ GeV.
