A soft X-ray enhancement has recently been reported toward the high-velocity cloud MS30.7 - 81.4 - 118 ( MS30.7 ) , a constituent of the Magellanic Stream .
In order to investigate the origin of this enhancement , we have analyzed two overlapping XMM-Newton observations of this cloud .
We find that the X-ray enhancement is \sim 6′ or \sim 100 pc across , and is concentrated to the north and west of the densest part of the cloud .
We modeled the X-ray enhancement with a variety of spectral models .
A single-temperature equilibrium plasma model yields a temperature of ( 3.69 ^ { +0.47 } _ { -0.44 } ) \times 10 ^ { 6 } ~ { } \mbox { K } and a 0.4–2.0 keV luminosity of 7.9 \times 10 ^ { 33 } ~ { } \mbox { erg } \mbox { s } ^ { -1 } .
However , this model underpredicts the on-enhancement emission around 1 keV , which may indicate the additional presence of hotter plasma ( T \gtrsim 10 ^ { 7 } ~ { } \mbox { K } ) , or that recombination emission is important .
We examined several different physical models for the origin of the X-ray enhancement .
We find that turbulent mixing of cold cloud material with hot ambient material , compression or shock heating of a hot ambient medium , and charge exchange reactions between cloud atoms and ions in a hot ambient medium all lead to emission that is too faint .
In addition , shock heating in a cool or warm medium leads to emission that is too soft ( for reasonable cloud speeds ) .
We find that magnetic reconnection could plausibly power the observed X-ray emission , but resistive magnetohydrodynamical simulations are needed to test this hypothesis .
If magnetic reconnection is responsible for the X-ray enhancement , the observed spectral properties could potentially constrain the magnetic field in the vicinity of the Magellanic Stream .