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Relaxation Oscillator Functioning

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Hello, I came across this Relaxation Oscillator topology but I cannot figure out its working. Can somebody please explain its functioning & how to derive its frequency expression?
 

l have been thinking about this and there are the basic equations that would define the circuit.


I have the circuit oscillating with L1=1mh & L2=10mh with coupling coefficient k= 0.999. With Drain & Gate capacitance of 1p & 10p. I have attached the netlist.

Code: 
*Spice netlist 
C2 0 C2_2 10p
C1 0 C1_2 1p
LPKT1 T1_1 C2_2 10mh
LSKT1 C1_2 V1_1 1mh
KT1 LPKT1 LSKT1 .999
JQ1 C1_2 C2_2 0 JNJFET
V1 V1_1 0 DC 0 PWL( 0 0 1u 0 1.1u 1 3u 1 4u 1 5u 1 6u 1 7u 1)
R1 0 T1_1 100

*Circuit Analyses :
.OP
.TRAN 1n 50u 0 5n

* Models/Subcircuits Used:

*NJFET 
.MODEL JNJFET  NJF()
.END

So Can anyone help me take it further? Are the equations correct?
How do we proceed to analyze this?
 

These magnetic oscillators work by the core saturation. The coupled windings couple until the core saturates and then there is no coupling.
 

But I don't think that a basic SPICE simulation will simulate core saturation? I see oscillations in SPICE, and I would want to analyze that.
 

I think the equations are correct. The next step would be to break the whole cycle into regions where we can break the JFET into regions of operation and solve these equations in those regions to calculate the whole cycle time period and hence the frequency.
I am thinking about this, will post as I progress. Seems to be a very interesting exercise.
 

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